WireIt is an open-source javascript library to create web wirable interfaces for dataflow applications, visual programming languages or graphical modeling, a simple example would be A Family Tree.
It was inspired by Yahoo Pipes and is used by Tarpipe. It uses the YUI library (2.6.0) for DOM and events manipulation, and excanvas for IE support of the canvas tag.
It currently supports Firefox 1.5+, Safari 2.0+, IE 7.0, Opera 9+ and Chrome 0.2.x.
Requirements: YUI Library 2.6.0+, excanvas
Website: http://javascript.neyric.com/wireit/