Launched: in Beta (since late 2004)
Location: San Francisco
Yelp is a website that allows users to write and share reviews of local businesses. It also has social networking features (adding friends, groups, etc.) to share reviews with a trust network. The idea is that people generally trust their freinds’ recommendations.
All of this user-generated content on local businesses, combined with the Yelp search engine, also provides great inventory for Yelp to sell local businesses contextual advertising.
The basics of Yelp: create an account, fill in your profile, add friends and write reviews. Yelp attempts to auto-fill the business information on a new review. The review consists of a 1-5 star rating and a free text area.
Searches bring up local businesses based on your zip code and include paid advertising above reviews.
Yelp is available only in San Francisco currently and plans to expand to other cities over time. They are also rumored to be closing on a Series A financing.