Lots of those in Kevin's and Stormbringrer's list are ones I still have the old sheet music to. I forgot about the Doors' Crystal Ship. That song was on the flip side of the 45rpm version of Light my Fire, and had some nice keyboard work in it. I learned it in the 70's, but have lost the music to it since then.
Some of those songs mentioned are pretty easy to learn if you know chords well, but some are really difficult, like Hotel California. Scott Davis has what I think is the best piano version of Hotel, you can find him playing it on YouTube and order the sheet music there as well.
I have the original sheet music to Total Eclipse as well, it sounds good
Stormbringer, just a few days ago I posted my cover of Goodbye Yellow Brick Road in the 40 Pieces a Year Thread.
You can hear it here if interested Goodbye Yellow Brick Road Cover
Some other thoughts
Michelle by the Beatles is really beautiful piano piece, I may put that one up soon on my 40 pieces a year thread.
Daniel by Elton John has some great and easy chord progressions and sounds good on the keyboard.
House of the Rising Sun is available in easy-to-more-difficult versions in several keys.
Bridge Over Troubled Water is long but a good piano piece, I knew it "back when', but haven't played it for 30+ years
Yesterday sounds great on the piano as well.
Morning Has Broken, Cat Stevens
Some pieces don't sound nearly as good as a piano cover, compared to the original, as you might think. I've got Benny and the Jets, but just don't like the way it plays. Jump is another one that just doesn't work for me on a piano, other than the famous short riff.
A couple of Simon and Garfunkle songs are in my favorites group
So Long Frank LLoyd Wright
Hazy Shade of Winter
American Tune (great/fast chord work, all in C)
I'm going to enjoy this thread!