Here's a listing of compositions outside of the realm of choral music. Some vocal, some piano, some others...

Away in a Manger, soprano/piano, available in a lower key, (video)
Be Still, piano (video)
Beethoven Symphony 5, mvt 1, piano duet (Available through Two Bridges Music Press) 
Come, Sing a Song*, unison, optional two-part, children's game song
He Lives*, piano/vocal
Here to Stay*, full musical; script, sheet music and mp3's available for free download
Lead Kindly Light/Poor Wayfaring Stranger, soprano recorder (or C instrument), piano
Love Medley*, soprano voice/piano
Midnight Dance, two marimbas (video)
Once in Royal David's City, bassoon and piano
Pomp and Circumstance in 7/8 and minor, piano
Symmetry, piano solos
What Child is This? piano, voice, cello 
What Child is This? saxophone duet

CLICK HERE FOR MY FLUTE AND PIANO COLLECTION