Altoon's Anthology of Graded Classical Piano Sheet Music is an anthology of classical piano sheet music, graded by difficulty level.  Various works are represented, such as Bach Two-part Inventions, Beethoven Fur Elise, selections from the Bach's Well Tempered Clavier, Chopin etudes, Beethoven Moonlight and Pathetique sonatas, some Mozart pieces, a Clementi Sonatina, The Entertainer and Maple Leaf Rag by Scott Joplin, Fantasy Impromptu and the Winter Wind Etude of Chopin, plus various others.  Comprehensive, 300-page public domain anthology, with pieces graded into categories of novice, intermediate, expert, master, grandmaster, and extreme grandmaster.