Download the new Yelp app (came out yesterday). So you shake your iPhone 3 times. That activates a feature called Monocle. A message should come up if you activated it. A blue box will come up saying "the Monocle has been activated." It will create a button in the top right corner. Now you should be able to look at the bars, restaurants, etc. Only works on iPhone 3GS.
http://friendfeed.com/scobleizer/e6e411b4/new-yelp-iphone-app-is-also-out-there-cool-easter
http://friendfeed.com/scobleizer/e6e411b4/new-yelp-iphone-app-is-also-out-there-cool-easter