Not that I wish to shill for a commercial endeavor, but as a beginner, I found this set of workshops to be very rewarding:

http://www.summerjazzworkshops.com/

Although I wasn't playing piano at the time, I met a number of classically-trained pianists that were attending as jazz beginners. There used to be (and maybe still is) an entire trac set aside for pianists in that category.

Guy