I can't remember if I've mentioned my fascination with outlining software before. Over the years, I have used PC Outline, ThinkTank, MaxThink, Lotus Agenda, Ecco Pro and probably a few others I've forgotten. Outliners were a niche product, and sort of died out after Microsoft Word added rudimentary outlining. I've continued to use Ecco Pro, but it was abandoned by the developer 6 or 8 years ago, and is now rather dated. I was trying to put some notes together the other night and got frustrated because it didn't support the scroll wheel on my mouse. Searching with Google, I found a great replacement -- NoteMap. This is a simple, single-pane outliner that does just this one task but does it very well. It's a little pricey -- they are marketing it to lawyers -- but no more so than Ecco or a few of the others I've used.
The funny thing is that I have probably used outliners less than any other category of software I own. But I wouldn't want to be without one!