Check out this site I found called Goldstar. They have half-price tickets and member reviews of concerts, sports, theater and more. Tons of events in NYC including wine tasting, Knicks and Nets Basketball tickets, boat tours and Broadway shows, all at significant discounts. I recently bought 2 tickets to see the Knicks and it cost $40 for $140 seats. No catch, just great prices! Check out the Yelp.com review if you're skeptical.
Direct Link to Goldstar.com