I guess we all have.
At the listed web sites you can find fake books and sheets to thousands of songs for guitar and for keyboard. Ready to download.
And you will find very powerful search sites, covering the contents in hundreds of fake books.
Million Dollar Collection of Sheet Music
mfiles - free notes Sheet Music
Classical Piano Free Downloads
Free Popular Piano Sheet Music
International Music Score Library Project
Carole Lorain Music Collection
English Songs and Movie Themes
Fiddle Tunes of the Old Frontier
Band Music from the Civil War Era
Nineteenth-Century Song Sheets
American Sheet Music, ca. 1820-1860
American Sheet Music, ca. 1870-1885
Berklee Library Fake Books Index
Music Library & Listening Center