In case you haven’t found it yet, here’s a great website for downloading and printing free sheet music for piano: MakingMusicFun. I visit it from time to time to supplement the teaching books I use, particularly when a pupil needs more practice at the current level before progressing to the next page or section.
They have a good selection of scores from beginner to intermediate. Although the music is organised into levels, there is no actual piece-by-piece progression so I wouldn’t recommend using it in place of a progressive course. If you want to learn to play the piano and make steady progress in a clear and logical manner, I would recommend something like the Alfred’s Basic Adult Piano Course. But the Making Music Fun website is a very useful additional resource.
Take a look – what do you think?