I’m a big fan of outliners, as I’ve mentioned in the past. A substantial portion of my life lives in shadowplan, the palm/windows/osx outliner, and I’m always looking at interesting new examples to play with. (As an aside, there is a fantastic series of articles that’s been running in About this Particular Macintosh called About this Particular Outliner that anyone even mildly interested in outliners should check out.) I’ve been tinkering with a couple of web-based tools lately: tadalist and sproutliner. They’re both well designed with clean, easy to understand interfaces, but sproutliner wins on features – it’s actually an outliner whereas tadalist is, as the name signifies, just a way to make lists. Anyway both are free and well worth checking out.