Yelp.com is a site that lets people review bars, clubs, shops, and nightlife in various US cities. Yelp only began to offer an API a few weeks ago and Walter Korman wasted no time in releasing a client library for Ruby. It's called, simply, "yelp" and lets you directly use Yelp.com's data from your apps. You can do cool things like search for business reviews, locate business reviews by business phone number, and search for neighborhoods by geo-points or address/location.