Itun
Try 911tabs.com, they usually have piano sheet music as well and ichigos.com
You can download sheet music for The Little Drummer Boy at the Holiday Sheet Music site http://download-sheet-music-online.com/holiday.html
In any music shop you can get books with piano music in it, and you can download it off the internet if your looking for a particular song.
musicnotes.com
Yes, there is piano sheet music for Avenged Sevenfold. However, there is no free sheet music. You will have to download or purchase the sheet music.
Download it at http://www.musicnotes.com/download/suite/default.asp?ppn=mn0074157&dltype=0
Where can you find the piano music sheet to...The Amapola
At the link below. Just download the music, open up the sheet music after the download is complete and print!
See Related Links below.
You will rarely find free sheet music legally available for copyrighted music.
http://www.sheetzbox.com/piano/sheets/download?i=NTQ1NA==
pandora.com