I send a lot of my students to IMSLP to browse sheet music and I thought it might be more convenient to have everything in one place. A lot of these scores are very long so make sure before you print anything that you are printing just what you need. Also, I find it very handy to load these scores onto my iPad (you can do this on just about any tablet/kindle/whatever the kids are into these days).
If I have missed anything or you would like me to try and find a particular score please contact me through the contact page (public domain music only please!).