TikZ and PGF are TeX packages for creating graphics programmatically. TikZ is build on top of PGF and allows you to create sophisticated graphics in a rather intuitive and easy manner.
Disclaimer: This site is not the official home of TikZ and PGF. Consult the Sourceforge project page for releases, support and bug reports.
Track the development of TikZ and PGF.
This package provides a macro for drawing trees with TikZ using the easy syntax of Alexis Dimitriadis' Qtree. It improves on TikZ's standard tree-drawing facility by laying out tree nodes without collisions.
A Java AWT/Swing Graphics drop-in replacement that renders to the TikZ/PGF (LA)TEX language.
A presentation about TikZ. Full source code included.
Video from TUG 2009.