Well, if you wanted a more pure just note-taking program, there are indeed more options out there. VoodooPad was mentioned... I'm using the latest VoodooPad Pro to make a synopsis of a book, and it's very nice, though you may have to get used to the wiki structure. Yojimbo is good, but again, it's an info gatherer more than note taker for school etc. (same as Caboodle).
If you want a super simple and extremely usable note-taking program I highly recommend xPad. It's free from here (PPC):
http://getxpad.com/
or you can get the paid UB version (works with intel) from macupdate or versiontracker.
It's brilliant - basically a window opens like in TextEdit, you write your stuff, and there is a sidepanel where all your other documents are listed, and can be color coded, categorized etc., so you have a constant overview of all your papers. Extremely simple and functional.
Then there's Scrivener - probably the best word editor if you're writing a longer project, like a book with chapters etc., it was coded by a writer for writers.
There are tons of options. Enjoy them, explore them. Good luck!