Here is a small collection of sheet music written in LilyPond:

• firth - the piano introduction to "Firth of Fifth", by Genesis, from "Selling England By The Pound"
• staendchen - Liszt/Schubert "Ständchen" (just the piano part, no lyrics, no ossia piu facile)
• gymnopedie1 - Satie, 1st Gymnopedie