Golum - Guy actually writes and sells separate poetry, not tied to his novels.
Last year when Alethea and I were editing Elemental (coming out via Tor in a couple of months) we talked to Guy about getting one of his epic poems in the antho but we couldn't quite get everything to align just right to allow it.
Guy's an amazing writer and his poetry actually goes a long way to showing just how amazing.
I've been wracking my brains for the last few hours trying to think of another fantasy writer who also does poetry - you have Steven Erikson who published a couple of books in Canada a few years ago under his real name... Steve Lundin... but I really can't come up with anyone else...