VoodooPad -- a desktop wiki
Voodoopad is a sort of desktop wiki/note-taking tool that you can type or sketch into.
VoodooPad is a sort of wiki for your (OSX) desktop. You can put in text, images, and sketch things out. I assume if you have a writing tablet you’d be able to use that instead of the mouse pointer to draw, and perhaps even to write out notes to yourself and let inkwell convert them to text… not sure though, I don’t have one. :-)
Free 15 page trial, but you’ll have to shell out $25 to get the real thing. It supports encryption, also, so your jotted down instructions for the doomsday device will be safe from those meddling kids and that darn dog. Just be sure to follow the advice on the Evil Overlord list and set your password to something the average 6 year old cannot crack on his first try.