learning process

Sometimes when I learn something new, I feel like I need to write some notes about it and organize them somehow in hierarchy (topic -> subtopic, etc).
Does anybody do the same things? What kind of tool or maybe web-service would you recommend for it?

org-mode

I find pen and paper quite satisfying.

>>2
*folds you in half and takes a bite out of you*

>>1
Duh, everyone does. I just use a text editor and try to use asciidoc when need on my Documentation. Unless I am not on a computer, I use a notepad or composition book to write notes.

I personally found that the Cornell note-taking system  works best for me, even for simple notes on text. Well, I used it before it was defined. Hehehe, so much so, my notes look like mini man pages.

I do take notes, but I use tagging instead of hierarchy.