Warning, Mac-centric answer:<p>For task lists, I tried a bunch of things at one point, and only one that stuck was Taskpaper (<a href="http://hogbaysoftware.com/products/taskpaper" rel="nofollow">http://hogbaysoftware.com/products/taskpaper</a>). It's so simple that I actually use it. I've been using it for about a year now on a sustained basis. It has simple emacs keybindings, like other OS X text editors, so that's nice for me too.<p>For ideas best expressed by complicated freehand drawings, I use pen and paper. I always carry an unruled (no lines) notebook for this purpose.<p>For a while I was using a small drawing tablet and Curio (<a href="http://www.zengobi.com/products/curio/" rel="nofollow">http://www.zengobi.com/products/curio/</a>) for drawings, but it didn't stick. The GUI was a little too slow, and plugging in the tablet was too much of an extra step. A tablet Mac would solve this. (Yeah, yeah I could get a PC, but I'd rather avoid it if I can.)<p>When I take notes at a meeting or a talk, I use TextEdit (again, w/ simple emacs keybindings), and depend on spotlight to help me relocate things. I prepend all filenames with the date in <2 digit year><2 digit month><2 digit day> format, so by default things sort by date across filesystems etc. This is surprisingly useful.