Last year, I posted my joyous discovery of Noteflight.com where I could use free software to write out simple music. I wanted to add here that Scorio.com is similar to Noteflight, though I only used it to find music.
So these two sites (and there may be others) give you the ability to
1) write music
2) search through what others write and make public, which includes some of my favorite pieces.