The score can be played directly from the browser, shared with individuals, published online or printed as sheet music for use by live musicians. Scores may also be embedded in other pages such as blogs or personal websites.

Here’s an example from the Noteflight site:

Note that this isn’t just a picture of music, but an interactive music display; you can select and listen to individual notes and measures.

Now available as a free public beta release, Noteflight says that it’s the first online application to fully support the editing, layout, rendering, playback and printing of conventional music notation.