The Subversion tree currently only has the source to their Flickr Uploadr tool, written in XULRunner, but that's a great start. The Flickr API is a beautiful thing. And, I'm happy that quite a few other sites have copied the basic structure of this Web Service API. Makes it easy to mash up solutions from web data. Hmm. Tasty. And simple. Like Skittles.
Flickr is currently processing about 700 API calls per second across 109 public API methods. Nice.