Fur Elise, Moonlight Sonata 1st mvt and Symphony No.5 1st mvt by Beethoven,
Ave Maria by Schubert, Toccata & fugue in d, Air in D and Jesu, joy of
man's desiring by Bach, The Ride of The Valkyries by Wagner, Eine kleine
Nachtmusik and Turkish Rondo from Piano Sonata in A by Mozart, Piano
Concerto No.1 Opening by Tchaikovsky, Chorus of the Hebrew Slaves by Verdi,
Finale from Overture (William Tell) by Rossini and The Flight of the
Bumble-Bee by Rimsky-Korsakov :)

Most of the works are hackneyed badly but you've asked for this:) ...
You'll have to find 6 more yourself (throw in some Vivaldi and Chopin:)

You can stuff 20 pieces in one CD only if they're MP3s.  Maybe you had this
in mind.

Juozas Rimas Jr (not the one playing)
http://artists.mp3s.com/artists/141/juozas_rimas.html