A wild feed (also 'wildfeed') is an unannounced, unscrambled broadcast via satellite of a syndicated TV program, or a special event, such as a sporting event or a news event. The are free (as in beer) in that they do not require a subscription to any single satellite service or any special equipment (outside of your satellite dish) to receive the transmission.
Wild feeds are used by television networks to provide content to their affiliate stations. Wild feeds are delivered on an apparently random schedule coordinated between the network and it affiliates; presumably, the affiliate has a better way of knowing when the broadcast is coming than an idle observer. The affiliate station picks up the satellite transmission and records the program or event. This allows the affiliate to broadcast the program when they want, in case it is preempted by another program (which happens a lot during football and baseball season in the U.S). It also allows the local affiliate to insert their own commercials into the breaks in the show- most syndicated programs are broadcast on a wild feed with no commercials, only 10-15 second "dead air" spots that multiple commercials can be spliced into for broadcast.
Wild feeds are broadcast over C-band satellite, a range of frequencies that is not normally available to the sorts of small dishes that satellite subscribers have. The necessary dish is between six and eight feet in flyover country, and between eight and ten feet on either coast- and dishes of this size are often regulated or banned by local zoning regulations, deed restrictions, or other rules and regulations. Buying a C-band capable dish is a substantial undertaking, even if it is legal in your neighborhood (or lack thereof). The dish itself sells for about $2000, not counting the cost of transponder, installation, subscription fees, and other equipment. Colleges and universities, as well as your local telecom monopoly have access to this sort of equipment, and it is from employees and affiliates of such institutions that information about (and sometimes recordings of) wild feeds trickle down to the rest of the populace.
Assuming one had equipment capable of picking up C-band signals, the transparent nature of a wild feed makes it relatively easy to capture. No Radio Shack home soldiered decoder cludges needed. Instead, one needs only know the name of the satellite where the signal is coming from, and the number and polarity (vertical or horizontal) of the transponder. One also needs to know when exactly the show or event in question is being broadcast. Fortunately, for popular television shows and sporting events, this information is tracked by a number of sources on the Internet, as well as in some dead tree publications aimed at audio/videophiles and satellite owners. Orbit magazine (www.orbitmagazine.com) is one such source, providing schedules for the wild feeds of popular programs. Note that there is often a little "wiggle room" in the transmission times; presumably, affiliate stations are given an early heads up about such last-minute changes, or are expected to keep their recording equipment running over a larger window. Civilian viewers often end up missing the beginning of a program, or thinking that they've missed in when it goes off late.
Culturally, wild feeds occupy a significant place in the world of raving, obsessive fandom. Wild feeds provide spoilers and early summaries for folks who are desperate to be the first on their block to find out what quasi-supernatural downer was visited upon Buffy and the Scooby Gang this week, or where Capt. Archer/Janeway/Cisco/Picard will be boldly going in the next 45 minutes. Of course, wild feeds are available for generally every syndicated program, not just those that have large, insane fan bases- but no one really pays attention to them. Shows that have substantial wild feed followings and interest include all of the recent Star Trek serials, Buffy the Vampire Slayer and its spin-off, Angel, as well as (oddly) formula 1 races. Some shows that depend heavily on suspense to bring in their audience (the various reality TV shows, for instance) do not make use of C-band wild feeds- relying instead on more secure and secret means of distribution, in order to avoid ruining the suspense of finding out which tiresome, attention-grubbing sociopath was blown out the airlock this week (we can hope, can't we?).