Our API directory now includes 40 reviews APIs. The newest is the Open Game API. The most popular, in terms of mashups, is the Shopzilla API. We list 27 Shopzilla mashups. Below you'll find some more stats from the directory, including the entire list of reviews APIs.
Apartment Guide has just announced a new partnership with Reputation.com in conjunction with the release of their Review API. The API enables Reputation.com to aggregate Apartment Guide's 190,000 Resident Ratings & Reviews for analysis and reporting purposes.