After beating it into shape with Paint Shop Pro 8 (Curves, luminance replacement via Channel Mixer, etc.). This is still no prize-winner, but the contrast is better and there is a lot more detail visible that was faded out in the original scan.

Awhile after scanning this image, I upgraded my scanner software to Lasersoft Silverfast 6, which should enable me to get better quality original scans and hopefully not have to do quite as much correction afterwards.