In my search for some software to help me with planning (or prevarication as it's also known!) I came across this very useful software
http://www.tiddlywiki.com/ It basically allows you to build your own wiki in a single file which you can either keep on your computer, send to someone else or publish on the web. I've got a contents list on the left (characters, settings, etc) which open up their own stubs containing text, tables, lists, images etc. I can also use tags within each stub to cross reference between items. It's pretty flexible and easy to use, is free and (I think) works on any system. The webpage itself is built using this so you can see what it's like from that. My one problem with it is that tables are tricky to do (you have to get spaces and returns exactly right)
Maybe too late for other nanowrimos, but it could be useful for lots of other things. I've just got to work out all the info to go in it now!