Despite all the XML abuse going around these days, there are is a small, but growing, number of web service consuming applications out there, and one very neat app I found is FlickrGraph (see my Flickr profile in it).
FlickrGraph wouldn’t at all be possible without the Flickr API, which exposes many of the funcionalities in Flickr as REST, SOAP or XML-RPC calls to any developer interested in using them.
This is what Jeff Bezos points out in his Web 2.0 talk:
Web 2.0, from where I stand, is about making the internet useful for computers.
Blogs with RDF/RSS/Atom-based aggregation were only a very tiny first step to making content and services more widely available, and now everytime I think of a useful service on the web, I end up sketching out its API first, figure out a few interesting uses for it, and then decide if it’s worth or not implementing.
If you look at Flickr’s insane popularity rise, there are definitely a few lessons to learn about a great web application, and providing an API is certainly one of them. It’s an incredibly dense app, even with the apparent simplicity, so I’m sure there’s a lot more.