You can find the notes for the Super Mario Theme at www.pianoloops.net under "Free Sheet Music"
Here are many ways of getting free sheet music, probably the easiest of which is to simply type 'free sheet music' into google, along with the name of the piece you require. However, this occasionally doesn't work, so here are some links to pages I have found helpful:
- www.gmajormusictheory.org (mainly piano and guitar music, but might have some others. Mainly classical)
- modernpianomusic.com (as the name suggests, all piano music, most of which modern. However, does charge for some music.)
- http//www.freesheetmusic.net ( various instruments, various styles)
- http//www.8notes.com (various instruments, different styles)