Ripcord is an PHP 5 XML-RPC server and client library with a very simple and easy to use API. You can create XML-RPC, (simplified) SOAP 1.1, and SimpleRPC clients with one call and then call RPC methods as if they were local methods of the client. You can create a server with one call, passing it any number of objects or classes whose methods it will publish and automatically document.
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).
spmfilter is a mail filtering framework. It attempts to be a general filtering framework for any purpose. The API enables spmfilter plugins to access messages as they are being processed by the MTA. This allows them to examine and modify message content and meta-information during the SMTP transaction. Plugins are loaded at runtime and can be processed in any sequence. The processing chain can also be altered by a single plugin, for example if the plugin has to stop further processing.
django-eve-proxy is a Django app that allows you to host an EVE API proxy that is open to Web requests or internal requests programatically. It honors EVE API cache expiration intervals and updates as needed (which means you don't have to worry about stuff like cachedUntil). You may also quickly and easily create a traditional EVE API proxy by downloading the proxy example, in addition to simply using the proxy capability from within your Django site.