Social sharing and networking site Friendfeed (friend to the hyper-connected mind you - see the compete.com data below) announced version 2 of their API is available for beta-testing.
New features include realtime API's (utilize long polling - which allows to emulate information push from a server to a client - to get feeds in real-time), flexible sharing of information (direct message users, share to multiple feeds), file attachments (attach images, PDFs, spreadsheets, etc.), OAuth support and a more simplied response format. Friendfeed provides the HTML for representing entries so developers don't have to construct it.
Documentation is available at http://friendfeed.com/api/documentation. A Python library that implements the new API methods and OAuth support is available at http://friendfeed-api.googlecode.com/files/friendfeed-api-v2-beta1.tar.gz.
Friendfeed has a long way to go to compete with the likes of Twitter. Perhaps this new API will offer some help.
Twitter vs. FriendFeed (June 2009):