1. a bag of apples
nice place, quite new. interesting collection. worth it. mostly for both melody and accompaniment.
2. animenz' piano sheet
been operated from 2009. great collection. just like j-madness, they also rating the difficulty. I tried randomly download a file. It was a singing sheet, only for melody and lyric is in hiragana. Want to sharp your Japanese?
3. sheet music swap
nice place but you must register to download. they also rank the difficulty so you know which one best for you. aside from anime, they also put other style of music.
4. yahoogroup: animesheetmusic
wow, i wish i know this place long time ago... recently not really active but i think still worth it to join. formed at year 2000, with thousands members. if it's a little silent, maybe it's time to make some noise again. i joined. why don't you?