Budget Travel - Cheap/Free tickets to events in major US cities

http://www.goldstar.com/

Some good deals in NYC eg New York Philharmonic, Harbor cruises etc.
also they will send you emails with offers for freeshowsifyou sign up

Has anyone actually used this besides the OP?

I have successfully used Goldstar for concerts and shows in Los Angeles many times in the past six months (most recently a couple of weeks ago to see "A Chorus Line" at the Ahmanson Theatre).