Bought one of these myself a few months ago for £5 and thought that was a bargain, this is the lowest I've seen it. As with any FM transmitter, bass reproduction is not great but at this price, you can't complain! Don't forget to go through Quidco to save another 5p.
The Hut's blurb:
Now you can use your iPod, PDA, MP3, CD, cassette player, PC, or laptop to listen to your favorite tunes through any FM stereo receiver. The Belkin TuneCast II Mobile FM Transmitter wirelessly connects portable music players to your car or home stereo quickly and easily using FM radio waves. Just plug the TuneCast II into the headphone jack of your iPod, PDA,MP3, CD, or cassette player; or connect it to your PC or laptop computer. Tune your car stereo or receiver to any clear FM frequency, and enjoy your iPod music experience with more sound and fewer wires.