Tiddlywiki works well on my n800. Other wiki engines work, too. Before
switching to Tiddlywiki, I used Python-based MoinMoin for taking
notes / keeping personal info. Like TW, Moinmoin works well on
multiple platforms.
A search of the forums at Internet Tablet Talk should turn up more
info...
http://www.internettablettalk.com/
Jeff Lee