I used to listen to a lot of metal for a few years, a lot of trance for about a year, now I'll listen to most anything. Current favorite genres are reggae, indie, alternative, folk and chillout.
Bands: Xavier Rudd, Motion City Soundtrack, The Arcade Fire, John Butler Trio, The Postal Service, Bob Marley, State Radio, Massive Attack, and Hooverphonic.
I know everybody tries to pimp their favorite artist, and while I could go on about all of mine, I would highly recommend Xavier Rudd to pretty much anyone.
Wikipedia link. He plays more than a dozen instruments, and is a one-man band with great messages.