Flickr, focusing on photo sharing, is one of the oldest community-driven sites out there. They were also an early adopter of web APIs for third party developers. These things have given them a large user base and a very rich API. Flickr Services is probably the most flexible web API we have seen. The API home page is located at http://www.flickr.com/services/api/. You will need a free developer key to use this API. As Flickr! is a subsidiary of Yahoo!, you will also need a free Yahoo! account. You will be prompted for both at http://www.flickr.com/services/api/keys/. From there, you can also sign up for both.
Like the other APIs from social-sharing sites we have seen, Flickr Services’ API focuses not only on their subject matter, but also has many methods that deal with community features. There are an abundant group of methods that allow you to query information about Flickr’s community. Assuming someone has allowed it on their privacy settings, you can get a person’s...