let me try to explain it by listing some of the things I want to do:

1. Submit random thoughts, notes, facts, and to-do tasks of any sort and at any time.
2. Tag each of these submissions freely.
3. Manage these tags centrally.
4. Associate meta-data with submissions and tags.
5. Search, filter, and sort submissions. I want lots of power here.
6. Display views of submissions (including within searches) in a hierarchy.
7. Create said hierarchies easily out by ordering relevant tags.

I'm thinking towards some kind of desktop program that allows me to quickly do all of these things. A web service could also work, too, but it will need offline capabilities. I don't want to have to pay for this, if that's possible.

Also, as I know regex and SQL, I wouldn't mind solutions involving the use of either.