Many folks don’t realize that it is possible to put a very low-power radio station on the air in the AM and FM bands without a license and without breaking any federal regulations. Under the FCC’s rule part 15 you can broadcast at low power levels in broadcast bands, which is what makes possible those little transmitters made for routing your portable CD player to your car radio. While transmitters of that type don’t go much further than across the room, with some clever engineering you can still broadcast to an entire neighborhood, all while staying completely legal.
In the past I’ve mentioned some part 15-compliant stations like WY2K in Springfield, IL and Allston-Brighton Free Radio that operate on the AM band, where the rules are less stringent than on the FM band. Just today I stumbled on this Master List of Part 15 Radio Stations of North America. It’s a very comprehensive page that gives links to known stations operating on broadcast and shortwave bands, in addition to an explanation of part 15 broadcasting in each band and links to manufacturers of broadcast transmitters and equipment intended for part 15 operation. For each station there are comments and descriptions of the stations, how they operate and their programming. If you’re interested in trying out broadcasting without taking the risks involved with unlicensed low-power/micropower FM, then this is something to check out.