I tried several of these and found some great stations. My favorite of those recommended so far is accujazz. If you haven't tried it, check it out. You can choose from a number of different 'stations' within the station to suit your mood, including be bop, classic, dixieland, smooth jazz, avant garde, piano, vocal, guitar, saxophone, etc. You can even choose by composer (well, at least some of the great ones), in the event you are in the mood for Monk, or music inspired by Monk, for example.
This station is just tremendous for jazz fans. I look forward to checking out more recommendations others have made. Great thread!
By the way, I can't remember if anyone has mentioned it yet but Pure Jazz is pretty decent as well.