Links:

Adam Crane - Viola - Mp3 sample from live recital September 14, 2003.
All Classics - Free classical music mp3 downloads: Pachelbel Canon, Bach, Mozart, Beethoven, Haydn, Handel, Chopin, Joplin, more.
Classical MP3.COM - List of many classical artists who have mp3s available, mostly on mp3.com.
Different Trains - A handful of mp3s by contemporary composers in California.
GMN.com Downloads - The Global Music Network has a selection of exclusive free mp3s.
Guitarist-Composer Jeffry Hamilton Steele - Several short classical selections and excerpts.
Late Gothic Keyboard Music - A few MP3s of pieces from a 1452 keyboard treatise.
OSRecords - MP3 files of a few original piano improvisations for sale.
Perso Flamenco & Classic - Flamenco & classical guitar mp3 files and scores.
Virtually Baroque - Baroque selections in mp3 realized with MIDI samples and pipe organ.
eClassical.com - Commercial site with a large collection of mp3s priced at US$0.49-0.99. A few free downloads change daily.