I’ve just found out about the International Music Score Library Project (IMSLP). They provide a brilliant website for finding free classical music scores and seem to just generally have a really good collaborative/community attitude. Here’s what they have to say on their website:

“We at the IMSLP believe that music should be something that is easily accessible for everyone. For this purpose we have created a music library to provide music scores free of charge to anyone with internet access, with several other projects in planning. IMSLP is also entirely collaborative, and all contributions are greatly welcome.”