FM transmitters such as the Griffin iTrip are a decent way to connect your iPod to your car stereo (assuming it doesn't have an Aux In jack or iPod dock connector attachment). In the United States, personal FM transmitters are only allowed a 200-foot range, but in the United Kingdom, they're not allowed at all.
That changes on December 8th, when the British Ofcom authority will revise its policy to get in line with the rest of the E.C. Devices that have not been officially approved for use in Europe are still illegal there, but Griffin and the rest of the "Made for iPod" crew are likely to try to get their devices approved for sale there as soon as possible, since there are probably a lot of people in Britain who've been waiting for the law to change.
At least one British online retailer is offering the device already.