Score editors have been around for ages. From what I’ve heard from my music teacher Encore is the editor, but for the occasional user it is a bit expensive with it’s $399 price tag. Then there is Overture, Finale, Sibelius, etcetera. And there is of course open source projects like MuseScore and NtEd, which you need if you’d happen to run i.e. Ubuntu.
Then I thought it should not be that insanely difficult to do score editing “google docs” style, web based, and with funky sharing options. Well, of course smarter people came up with that idea long ago. Noteflight is an online score editor, written in Flash. I’ve tried it a bit and it is pretty easy to get the hang of, especially once you get a grip of the keyboard shortcuts, which is true for all score editors. For me as a lousy student, the free version, limited to 10 scores and a few other limitations is fine, and for somebody who’d like to build a private or shared library the yearly $49 seems not entirely unreasonable to me.