Aozora (青空文庫) [Archive.org URL]

インターネットの電子図書館.

This site is completely in Japanese and is above my level, but I think it is an online library of Japanese writings that are no longer covered by copyright. There is no listing by level of difficulty but I guess all of the entries are for more advanced students. A downloadable ruby .zip version or an HTML version of each entry is available.