Not really a substitute for a shorter commute, but you might try this:

http://www.amazon.com/The-Guide-Building-Classical-Collectio...

Caveats: - Published in 1999 so I don't know how available the albums are. - Classical is really sensitive to dynamics, and cheap car stereos suck at same. You turn up the volume to hear the quiet parts, then get blasted by the loud ones. I don't have a good car stereo, don't know how much it would help. Earphones are much better, but I don't know about driving with them.