Use this PHP library to interface with the App.net's Stream social networking API. Access application functions like: social graph, messaging, and places. Documentation, including code examples and access to other libraries is available on the library's GitHub page. Note that the API is in development and the library continues to be updated. The developers note that some updates may break backward compatibility for older versions.
If you're using Twitter's Search API via the api.twitter.com sub-domain, you have a week to switch to search.twitter.com, according to a post from Twitter's Taylor Singletary. The endpoint being removed has not been officially supported by Twitter, though other supported calls use the same sub-domain.
Socialmod is a system to either automate or simplify your site's social content moderation. Its socialmod API allows for direct integration of socialmod into your site, making using their service far easier. Its service has been used for such high-profile sites as the BET.com awards, as described in its blog.