GtdWiki
From 43FoldersWiki
GtdWiki is a version of PhpWiki with some special tweaks for implementing the techniques in David Allen's Getting Things Done. I've been working on it and using it for the past few months and I've found it to be pretty useful as a tool for implementing GTD.
I've included a "santized" version of my page setup which should make it pretty easy to get started
You'll need your own Apache/PHP server to set it all up. It also works best if you have a MySQL database to run it from, although it will also run from a flat file. Its not as easy to set up as something like Instiki, but you shouldn't have too many problems if you follow the instructions.
