As the existing Wing Chun
writeups seem mostly concerned with the history of Wing Chun, this writeup will attempt to provide an overview of what Wing Chun actually is.
First, a few words about my experience. Basically, I have been taking lessons in Wing Chun at my college (coincidentally, from the same place that the initial Wing Chun writeup comes from). I have not been doing it for very long, so I will probably be missing some (many) things.
Essentially, Wing Chun is how to beat someone in a fight very quickly. When I was describing it to a friend, I told him that the entire point to Wing Chun was "to get past an opponent's defences, and then hit him in the head, very hard". There are, as far as I know, only 5 kicks used in Wing Chun, and they are used mostly for distraction.
The basic method of attack is to strike, either with palm or fist, straight out. This uses your arm's tricep muscles, which are built to push things. This is also the technique behind the famous one inch punch. I have had this used on me (while I was holding something thick and padded in front of my chest, thank Eris), and it is very impressive. I was knocked over, and knocked over the person behind me who was supporting me.
Update (3-21-2002):I realized I forgot a very important point about offense and defense. That is the concept of keeping control of the center line, the area directly in front of your body. The reason for this is that, obviously, the shortest path between two points is a straight line. So if you can control that area, you can force your oppenent to go around to the side, giving you plenty of time to block their attack.
It is designed to be easy to learn (as mentioned elsewhere), it takes most people 2 to 3 years to learn all the forms in Wing Chun; after that a practicioner spends time refining their techniques. My Sifu has been doing it for about 15 years, and is frighteningly good.
An intersting aspect of Wing Chun is that it is very ugly to look at; the martial arts one sees used in movies like Iron Monkey and The Matrix are much more fun to watch. However, Wing Chun is designed for, and useful at, beating someone in a fight, should you feel the need for that kind of thing.
Bruce Lee studied Wing Chun, and one can see many similiarities between Wing Chun and Jeet Kune Do, the martial art he invented. In fact, I originally got interested in Wing Chun because Spike Spiegel, of the anime Cowboy Bebop, is a master of Jeet Kune Do, and, sadly, there are no Jeet Kune Do studios in Baltimore.