I hate to agree with Butthead, but I think about everything in hierarchies. I normally write everything down in a text editor tabbed out like a programming language, but I decided that I needed something a little more organized and easy to move stuff around (though nothing is normally as fast as cut and paste, to tell the truth)...
So I just downloaded and tried the Java Outline Editor (JOE) again and I must say that it rocks! It can import/export plain text tabbed documents into the outliner as well as more detailed OPML docs. I am hooked. I tried this app earlier in the year and didn't like it for some reason (I think it had a lot to do with the default green colors - the defaults are much nicer now). But now I'm playing with it again and I like it a lot. It even has a "post to the web" feature with some PHP Script... I'm going to have to take a look at that, I'd LOVE to put my to do list somewhere on my website as a central accessable repository for stuff like this.
As with all new toys time will tell whether it becomes a part of my daily routine or not, but right now it looks good. And maybe it's this newer machine I'm using at work, but Swing isn't dogging it at all (and I'm on JDK 1.3.1)... Pretty neat.
Later... playing with JOE some more and I discovered the integrated XML-RPC engine. Rock-on. I'm going to see if I can write up a quick XML-RPC get/save service for my website for to do lists. Centralized info, that's cool-as-hell.