App recommendation

[Michael Hipp]

I've become interested in outliner/freeform database/note taker/knowledge manager applications.  (These apps defy easy description.) The most famous example I can think of is AskSam. There's also ActionOutline and Ultra Recall. All are Win only. Does anyone know of anything comparable for Linux or (even better) multiplatform?

Links below if you're wondering what on earth I'm talking about.

Thanks,
Michael

http://www.asksam.com/
http://www.actionoutline.com/
http://www.kinook.com/UltraRecall/