Links to useful sheet music sites

In this topic I will list some nice sheet music sites. You are of course free to reply with other links to useful sheet music sites so I can edit the post to add more links.
Anyways, here are the links so far:

NinSheetMusic
This is a very useful site for fans of video game music. It contains lots of video game music pieces that have been arranged for piano by some of the site members. It contains .mus files that can be opened with any Finale program (Finale Reader can be downloaded for free, here:
http://www.finalemusic.com/Reader/). There are also midi files that you can listen to it if you want.

G Major Music Theory

This site contains lots of well arranged pieces, there are both classical pieces, traditional songs (such as national anthems and kids songs) and pieces composed by the site owner. All the pieces are arranged from difficulties ranging from 1st pieces to Intermediate level 4. Another great thing about this site is that all the pieces contain fingering suggestions.

IMSLP

This site contains lots and lots of public domain sheet music. Actually the goal of the site is "to create a virtual library containing all public domain music, as well as music from composers who are willing to share their work with the world without charge. " A lot of the sheet music is kinda old and doesn't look that well and if that bothers you then you might instead want to go to the site suggested below.

The Mutopia Project

This is another site of the same type as IMSLP but better, well, at least in some ways. The selection of sheet music on this site is steadily growing but is nowhere as big as on IMSLP. This site mainly contains public domain sheet music just like IMSLP but the difference is that the sheet music here looks nicer and that you can download midi files to listen to or look up some extra info about the sheet music and more.

Final Fantasy Music & Video Game Music

The title says it all. It contains sheet music, midi files, lyrics (for the few FF songs that actually have lyrics in them) and list of tracks in the soundtracks for some of the Final Fantasy games. Almost all the sheet music from FF5 to FF11 is there but the rest of the FF game sheet music is missing. The bad thing when downloading the sheet music is that you download .png or .gif images of the sheet music instead of .mus or .pdf files but I think almost everyone is printing out the sheet music anyways.

Jytte's Piano Sheet Collection

Jytte's website has plenty of sheet music that is graded and has sometimes Youtube videos or .midi files included. Check this thread for more info.

Thanks for sharing, Rickard.
I had a look. I really like the Mutopia Project, although it's mainly difficult things - but maybe I'll get to play those one day