Kiteboarding is the latest extreme sports craze. Combining elements of wakeboarding, snowboarding, windsurfing, and paragliding, kiteboarders use very large kites to pull themselves across water or snow. As I live on the coast, most kiteboarding that I'm familiar with is done in the water, and most kiteboarders are ex-windsurfers or ex-wakeboarders.
There are two main advantages to kiteboarding over windsurfing: a steeper learning curve and, of course, hang time. In the hands of a trained instructor, it's relatively easy to learn; unlike windsurfing, which can take weeks to learn to uphaul and water start (translation: be able to ride successfully), with proper instruction, a beginning kitesurfer can be up and putting around in a matter of days. But the really attractive part about kiteboarding is that the kite is able to pull you very, very, VERY, high into the air. Most professional kiteboarders are able to jump over 40 feet high, and world record for kiteboarding hang time stands at over 30 seconds (Erik Eck gets 35 seconds of hand time in the video 13 Daze).
Using a big kite to pull you around is nothing new. Benjamin Franklin once tied a kite to his foot, and used it to pull him across a lake while he floated on his back. In areas with large flat beaches, like parts of New Zealand, Jacksonville, Florida and parts of the UK, people have been using performance stunt kites to pull themselves around on small three-wheeled buggies for quite some time. Kiteboarding was developed in the mid-90's in Hawaii, Oregon, and France. It was popularized in Maui by windsurfing and wakeboarding legends like Robby Naish, Lou Wainman, and Elliot Leboe.
The kite is, obviously, the most important piece of equipment in kiteboarding (otherwise it would just be boarding!). There are two main styles of kites, ram-air and leading-edge inflatable.
Leading-Edge Inflatable kites, LEI for short, have an airtight bladder running across the leading edge of the kite, as well as several struts across the canopy, which are inflated with air to form a rigid frame. Since the frame is made up of air, it adds very little weight to the kite, and most importantly, makes the kite float if it crashes in the water. With a little practice, it is possible to relaunch a LEI kite that has been crashed in the water, because it floats and retains its shape. atlas says that with the leading edge deflated, LEI's make mighty fine rafts when the wind dies.
Ram-Air kites are inflated by the air moving through them, they have no rigid frame (see the hard link for more info). They are typically not used on the water because if you crash them, there's no way you can relaunch them. However, they are the norm on snow and other land-based applications because they are more efficient, handle better, and there's no bladders to pop if you crash it into a thorny bush.
Regardless of the type, the shape of the kite plays a big role in the handling characteristics. Aspect ratio is a common measure of the shape of a wing, and plays a big part in the way a kite handles. A High aspect ratio kite is long and skinny, and is usually fast, delivers a lot of pull, and jumps very high. A low aspect ratio kite is short and fat, doesn't pull as much, doesn't jump very high, turns a little better, and is usually suited to beginners.
The size of the kite is also very important. Kiteboarding kites are big. Very big. Just how big depends mainly on the wind speed, rider's weight, rider's skill, and type of kite. Kites are measured by the area of their sails when lying flat on the ground. Most LEI kites range in size/area from 5 m^2 to 20 m^2, with 12-14 m^2 being fairly popular sizes (this, of course, depends on prevailing wind speed in that spot). I weigh 135 lbs, and I usually use a 14 m kite from 14-16 mph wind, a 12 m kite from 17-22 mph, and a 7.5 m kite from 23-30 mph wind. Ram-air kites are usually smaller, because they are more efficient.
But the most important part of the kiteboarding kite is the ability to control it. They have at least two lines, attached to the left and right side of the kite, which are connected to a bar that the rider holds, allowing the rider to control the flight path of the kite (like a stunt kite). Pulling the bar with your right hand, will make the kite turn right, and pulling the bar with your left hand will make the kite turn left. Muscling the kite around with your arms is extremely tiring, so the bars have a loop, which can be hooked into a windsurfing harness. The harness looks like a big belt, kind of like the ones that professional wrestlers fight for, with a beefy hook on the front; some harnesses have leg straps, kind of like a rock climbing harness, to keep the belt from riding up to your shoulders.
Most kites have four lines on them, which allow the rider to control the direction that the kite is flying, and the amount of power the kite produces. Here is a very simplified version of how this works. Lines are attached to the leading edge and trailing edge on both sides of the kite. The trailing edge lines are connected to the right and left edges of the bar, and are used to control the direction of the kite. The leading edge lines pass through a hole in the center of the bar, and are connected to the hook on the harness. By pulling the bar towards the harness (and you), you effectively lengthen the leading edge lines in relation to the trailing lines, increasing the angle of attack of the kite, resulting in more pull from the kite; pushing the bar away from you will shorten the leading edge lines in relation to the trailing edge lines, decreasing the angle of attack, and giving you less pull. It sounds complicated, but it's really not. Imagine holding your hand out the window of a car. With your palm facing the wind, it is pushed backwards strongly, but as you tilt your hand into the wind, the push decreases.
On the snow, a plain ol' snowboard is used, nothing fancy or specialized about it. On the water, though, things get a lot more complicated. There are two main kiteboard designs out there right now, twin-tips and directionals. Twin-tip boards are more common, and look an awful lot like wakeboards, and evolved directly from them. Directional boards look more like windsurfing boards or surfboards, and evolved from windsurfing boards.
Twin tip boards are more commonly used, and resemble wakeboards. Your feet are kept permanently in place by full-blown wakeboard bindings or simple foot straps. These boards look like wakeboards to the untrained eye, but are lighter and have less rocker; while wakeboards are designed to jump off wakes, kiteboards are designed to edge upwind (more on this later). Twin tips have very low volume, (hell, you can use a piece of plywood), and don't really float. Instead of floating like a surfboard or a windsurfer, they require a strong, fast pull from the kite to plane across the water, like water skis. Right now the trend is in shorter boards - twin tips usually range from 120cm to 160cm in length.
Unlike a windsurfer or sail boat which use a large fin to pull against the wind, going upwind on a twin tip requires the rider to lean heavily on the edge of the board. Just like a snowboard or a pair of skis, the edges of a twin tip kiteboard are fairly sharp, and "cut" through the water; there are some small fins on the bottom of the board to help cutting through choppy water, but the upwind power comes from the edge. Most twin tip riders lean way back, with their butt barely skimming across the water, with the board almost vertical, 90° to the water. It's easy to keep the edge planted in the water this way, and it results in a really bitchin' rooster tail.
Directional boards are used mainly in waves, and resemble a windsurfing board. They usually have footstraps, like a windsurfer, and must be jibed to change directions. These boards are usually higher in volume than a twin tip board, and are usually ridden on the fin, like a surfboard or windsurfer. Directionals died off for a while, although they are now making a comeback, as some very talented people are exploring the possibilities of using kites for tow-in surfing. Some people are using regular surfboards, and some people are using kite-specific boards with footstraps. It will be interesting to see where this trend goes.
When the wind is too light to ride a regular kiteboard, but you're at the beach with all your pals and gear, all sorts of boarding experiments take place, occasionally with a modicum of success. When the wind is light, I like to go out on my 8' mini-longboard and cruise around. I have also tried riding skimboards (result: sand-burn on my ass), and wakeskates, which is like a small wakeboard with no bindings that can be ollied and kickflipped like a skateboard (result: sand-burn on my ass).
Then length of the board plays a part in the size of the kites used, and the wind you can ride in. A larger board with more surface area will plane faster, which will help you out in light winds or when your kite is too small for the given wind speed. In high winds or in situations where you're overpowered, though, a big board is very hard on your ankles, and difficult to control. Likewise, a long board is difficult to control in the air, especially when you're doing those inverted 720° spins with a between-the-legs handle pass.
So, all this equipment information is great, but where do you go kiteboaring? You need a beach where the wind blows towards the shore. You don't want it blowing offshore, because if you crash, you're headed out to sea; you also don't want it directly onshore (perpendicular to the beach) because it makes it hard to get going. I personally like a wind that is about 45° to the shoreline.
As for the water conditions, some people like to ride big waves, and others like to do tricks on flat water; either way, choppy water is the enemy - it makes it hard to keep your edge in, and it's hard on your knees. I personally like playing in knee-high or waist-high waves (what windsurfers often call "bump and jump" conditions) because they act like moving quarter pipes and double jumps. Fun.
I have had limited success kiteboarding on snow, but it is quite popular in parts of the French Alps, and on frozen, snow-covered lakes worldwide. There is a video floating around the web called "Chasta Show," which is absolutely amazing. (http://www.google.com/search?q=%22chasta+show%22)
If you'd like to learn to kiteboard, and I suggest you give it a try, take a lesson. There are many professional kiteboarding schools out there, which will get you up and riding quickly, and teach you to kiteboard safely. Kiteboarding is not something that I'd recommend you teach yourself, it's just too easy to do something stupid when you're inexperienced; you will injure yourself and put others at risk. Please take a lesson. Check out Real Kiteboarding Schools at http://www.realkiteboarding.com