wom_wiki + wom_docit
I wrote a plugin (and a replacement for classTextile.php) to add wiki features to TXP. Full details in wom_wiki
Suggestions are welcome but be polite, is my first approach to both textpattern plugins and PHP.
2006 update: I moved to a python wiki engine and implemented a blog mechanism on top (a lot easier considering I don't have a clue about PHP). You may want to have a look at the old code just for fun.