evernote
something much more, and a little less than one note. it is free to try and is by far the most used note taking app i have. i have the premium plan, which is 5 dollars a month. a little known feature of evernote is that your 1gb upload per month (on premium plan) is cumulative. in other words, if you make full use of upload amount each month, at the end of four years of college, you'll have 48gb of info stored in it. excellent syncing features.
voodoopad
a personal wiki. you create the organization scheme, so not as easy to get started with as onenote, but much more customizable. a very cool feature is that anytime you write or have written a word thatmatches a page name, it automatically provides links to it throughout. for instance, i made a page for a historical figure, and now every instance his name appears it is linked back to that master page. you can make links in one note, but it won't do them automatically like this. pretty good syncing features. free to try.
devonthink
i never could get into this one, but many people swear by it, and i admit that it sounds brilliant. free to try. i wish i cold say more, but i got hooked onto evernote before i could explore it.