Read the lyrics to the album As The Roots Undo by the band Circle Takes The Square. Incredible stuff. Every Time I Die's older albums have some great lyrics too... specifically the albums Last Night In Town and Hot Damn! The Blood Brothers also had a lot of great lyrics.... that's 3 good examples in the punk/hardcore area.
For hip hop there's Aesop Rock, Sage Francis, Saul Williams, Illogic, etc... lots of indie hop stuff has really great lyricists.
For modern rock, I think Thrice and their vocalist Dustin Kensrue write some nice stuff.
I honestly can't think of much metal that has lyrics even remotely interesting, creative, or intelligent. For the most part, I listen to metal for the musicianship, not the lyrics... Sad, but true.