Wrox’s Beginning Flickr Mashups is one of the first books available that teaches web developers how to build innovative applications with public APIs.  Expert Flickr developer Dave Wilkinson skillfully guides readers through mashup fundamentals including REST, XML, and Ajax and then on to creating their own mashups and remixes using the Flickr API.  Topics covered include: <ul type="disc">

Using mashup technologies including REST, Ajax,  JSON, SOAP, XML-RPC, CSS and more

Using Flickr API Objects such as Interestingness, Tags, Sets, Groups and others

Remixing Flickr with Flickr feeds

Remixing using the API

Greasemonkey hacks for Flickr

Geotagging mashups with maps

and more.

Companion website at Wrox.com includes source code.