A couple of days ago, I mentioned Tetsuo Kogawa's MicroFM transmitter, a simple one transistor FM radio transmitter. Tonight, I decided to put it together on an experimenter's breadboard. I didn't have the 2SC2001 transistor that Tetsuo Kogawa used, so I just dusted off one of my $.10 2N3904 transistors, and dug the rest of the components out of my junk box. I assembled it in the worst way imaginable, with no real attention to lead lengths (I left them all uncut) and fed with unshielded cable. It "worked", after a fashion at least, but I counted four images of the transmitted signal up and down the FM broadcast band.
I suspect if I built this properly on some copper clad with short line lengths, it would work better, but I suspect that it still would be rather horrible on spectral purity. As such, it's worth experimenting with, but I wouldn't try to build something this simple and try to get range beyond my desktop.