Here are some legal websites offering an assortment of free music
8Notes - Has a variety of different styles of music. The images you try to print will not be the best quality, but it is better than paying for the .pdfs of the music.
IMSLP - The granddaddy of free music sites, IMSLP is a library of all classical music in the public domain. Consequently, you won't find music from the past 80 years here.
MusicNotes - Though only a small selection of free music, it varies by month and is of good quality.
Free-Scores - With wide variety of music (with a fair share of it from different countries), Free-Scores has those hidden gems if you look long enough for them.
FluteTunes - Specifically for the flautist, this site has solos, duets, trios, and more for the flute player.
LDS Music - Though associated with the Mormons, many traditional hymns can be found on this site.
MUSOPEN - Similar to IMSLP but a little easier to work around. There is, however, a smaller selection of music here.
SheetDownload - I'm going to be honest, I don't know how this is DCMA compliant, but it is. At this site, you can find piano music of the top 100 pop tunes.