I was thinking the same thing. I know of a bach chorale book setup for piano or organ
(371 four-part chorales for piano or organ)
you can preview the book here:
http://books.google.com/books?id=dsTKO3 ... navlinks_s
It might not be for everyone. I originally bought it as a kind of sight reading practice.
There are a great many Baroque organ chorales by Bach, Pachelbel, etc. that are written for manuals only and thus can be played on the piano. Also, you could 4-voice settings of the psalms.
But this may not be the kind of thing you are looking for.