Indeed the FM things are illegal, but who's going to check??!?!?!
I'm not a huge fan of the Ipod I'm afaid - have you heard of Apple's so called "dirty little secret" - you can't change the battery!
Also, they're not worth the money (IMHO) - my pocket PC plays MP3s, cost about the same, AND I can surf the internet and watch videos on it too. (Fair enough it doesn't have as much disk space, but who actually has 9000 MP3s to listen to anyway?!)
PS. Tape adaptor all very well if your car has a tape player.....
Is there a legal alternative for cars without?