“Groovy Motherfucker”

Flickr now serves up Panda APIs so you can build your own rainbow-vomiting app. (Don’t forget that Flickr feeds also come in LOLCODE flavours)

Moo’s printing services made available through an API. Generate the graphics and text you want, shove em over to Moo as XML, and they’ll handle the checkout and fulfillment. (Revenue sharing is promised for the future)

Flickr’s API includes LOLCODE as a return format. Duly noted for any APIs I might create in the future…

Brilliant use of Google’s newly-exposed Gmail API to seamlessly blend to-do lists into your Gmail UI.

Wesabe have created an open API to allow folks to hack on their bank account data. I foresee some stonking visualization work coming out of this that will put Quicken, Microsoft Money, etc to shame.

The new Facebook API. They’ve done a really good job of letting you integrate — essentially they’re being a platform and then getting out of the way of whatever you want to build.

Python library for working with Google’s GData web services (Calendar, Blogger, Picasa et al)

Google Calendar has an Atompub-based API.

Very attractive presentation by Shaun Inman (author of Mint) on the benefits of building an API into your webapp.