The EDCommon framework extends Foundation and AppKit in a natural way. It contains common methods you always need, like removing whitespace around a string, special collection classes such as stack or object pair, an object-oriented API for socket programming, some widgets, the chasing arrows to indicate background activity for example, an XML parser and other nifty stuff.

http://www.mulle-kybernetik.com/software/EDFrameworks/download.html#EDCommon