I'll second Tom Holt. Hysterically funny. Of course, if funny is your thing, Terry Pratchett is your man, all of his stuff is good, but when he really got going with Ankh Morpork, it became legendary. I mean, Corporal Carrot, the 6 foot 4 dwarf constable?
I second Terry Pratchett's Disc World books. No one does humor and light fantasy better than him.
If you like a mix of humor and seriousness, I also recommend Lois McMaster Bujold. Her works are full spectrum, often able to combine humor and pathos.