Take one part Facebook, one part Yelp, and one part TripAdvisor. Stir in some Wikipedia, and add a dash of Twitter. You might end up with something a little like Lunch.com, which is debuting today at the Web 2.0 Expo show in San Francisco. It’s still in private beta, but the Lunch folks have offered to provide a limited number of invites to Technologizer readers. To get signed up, go to Lunch.com. In the Sign Up box on the right, click on the Click here next to Have an invite code? Then enter Technologizer as the invite code and your e-mail address–you’ll get an e-mail explaining how to take it from there,