APIcaller is a class that helps you to build API wrappers. You don't have to worry about building URLs, or even about parsing the requested data. As an example, if an API requires an API key, you can set this key as a default value and it'll be always sent with the API request. The API needs to return the data in JSON format, otherwise an execption will be thrown.
AS2Secure is a PHP library that allows you to send and receive AS2 (Applicability Statement 2) messages from partners. The project is split into two parts: a client to send one or more documents to a partner and a server to receive one or more documents from a partner. Its main features are asyncronous and syncronous MDN, partner setup, digital signatures, message encryption, secure transport (using OpenSSL), support for SSL client authentication, and multiple attachments (AS2 1.2).
Videopian is a PHP class that allows you to get any kind of information (such as title, description, author, duration, or flash player URL) about a video hosted on a video sharing service, just by its URL. The currently supported services are Blip, Dailymotion, Flickr (API key required), Google Video, Metacafe, MySpace, Veoh (API key required), Vimeo, and YouTube.