Of the pedals I've had/have, the MXR M134 is the best IMHO. Warm & lush sounding, with flexible controls that actually do something.
I've also had/used (in rough order of preference) Boss CE-2, Boss DC-2, Boss CE-3, Rocktron Tsunami, Boss CE-5, Rocktron Deep Blue, Boss CH-1 - all of them have a clean nice sound (which is mostly what I use a chorus for)
Not got to many of the "boutique" pedals (since I got the M134 I haven't really looked elsewhere) but the one pedal I'd avoid is the Voodoo Labs Analog Chorus - over-rated pile of junk that adds a nasty midrange "spike" to the sound. I can just about live with it on the clean channel/neck pickup but borderline unuseable with the bridge pickup or on overdriven sounds. Recently been discontinued, but don't rush to snap up one of the last ones...