I myself play the mandolin, which is a pretty commonly used insturment in blue grass. I reccomend the following for some good bluegrass bands/players.
Ricky Scaggs- lots of people say hes the best mandolin player around ever, I say hes the 2nd best
Yonder Mountain String Band- a really good bluegrass band, really good, went to see them and string cheese incident at Big Summer Classic last year, they do some classic blue grass, and some covers of other songs like crazy train and some system of a down songs
Indagrass- if you can find any of there music, its good
String Cheese Incident- some of its blue grass, some of its just jams and stuff
David Grisman- probably one of the best mandolin players of all time, just really good music all around with him
Garcia Grisman- Jerry Garcia and David Grisman's band from awhile back, very very good. If you like Grisman by himself, then him playing with Garcia makes it that much better.