As Gigantic Debaser mentioned, IMSLP is the best place to look for sheet-music.
Even professional musicians do that, conservatoires use it as well.
However, I have got a useful link for neo-classical chamber music, one of my favorites.
Ólafur Arnalds // Sheet Music
Here is an interesting
PDF of a rework of Nils Frahms Me and You for ensemble.
If you're good with music theory, I'd recommend transcribing or covering songs.
Perhaps these artists will inspire you: Einaudi, Ashram, Ataraxia, Corde Oblique and Lisa Gerrard.