I'd like to share some great collections of intermediate-level piano repertoire. All of these have a great variety of pieces from each of the four musical periods, and I have personally used them and recommend them! I know there are many more out there - if you have favorites that you use in your teaching that aren't listed here, please share! We can all benefit from recommendations from other teachers. And don't miss some recommendations for great intermediate pieces (and audio/video samples of each piece) here. Click on the pictures below for more information on the collections.
Succeeding with the Masters - FJH Music
These generally go from Late Elementary to Late Intermediate levels.
Baroque Era, Volumes 1 & 2; Classical Era, Volumes 1 & 2; Romantic Era, Volumes 1 & 2
Easy Classics to Moderns (Volume 17 of the Music for Millions series) - Hal Leonard Publishing; compiled & edited by Denes Agay
59 Piano Solos You Like to Play - Schirmer
I suppose some of these pieces may be considered "Early Advanced," but this is a wonderful book with great teaching repertoire!
Applause! Volumes 1 & 2 - Alfred Masterwork Editions
Great collections of showy, fun-to-play repertoire.
Music by the Masters - Alfred Publishing
This is a book I used as a young student - it has a great variety of intermediate classical repertoire.
Keith Snell's Piano Repertoire - Neil A. Kjos Music Company
Levels 3 through 7 are Intermediate levels
This is an awesome series - I love how it starts with the Preparatory level for very young students!
Celebration Series Perspectives - Frederick Harris Music
Great series that has ten levels of repertoire books and ten levels of etude books, as well as student workbooks.
Encyclopedia of Classical Music - FJH Music
This is a relatively new collection (published in 2005) that I LOVE - it has a wonderful selection of pieces that have really motivated my students to practice.