Schubert has written a number of delightful pieces for piano, including several Impromptus. This one is a challenge to play convincingly but worth the effort to practice. It is the second impromptu from his first set, catalogued as Op. 90 or D. 899. Download the PDF sheet music, midi and mp3 files for this piece using the links in the left-hand menu.
You can get the complete set of Schubert's Impromptus (Op.90 & Op.142) and Moments Musicaux (Op.94) from these links at Sheet Music Plus and Music Room, and there is a larger Dover edition containing Schubert's Shorter Works for Piano Solo currently available from Music Room.