Tumblr allows bloggers to post multimedia content. From photos, GIFs, and TV shows to jokes, Spotify tracks, and videos. The official library available in PHP allows interaction with the API, which can read Tumblr data to write a Tumblr post.
Gowalla, the location aware social networking service, has announced the release of their first public API (our Gowalla API profile). This will help them keep up with other location-centric social services like Foursquare's new API.