mp3gain
I listen to MP3s in the car and it's annoying when the volume isn't normalized. I can't be fumbling around with the tiny buttons on my MP3 player to adjust the volume while I'm driving. I found mp3gain and used it on a bunch of files and it appears to have worked.
If anyone knows of a better program for normalizing volume of lots and lots of MP3s, post now or forever hold your peace.

Why are you looking for something “better”? What's missing in mp3gain? I'm using it for years (`mp3gain -a album/*`). The only thing that would be cool: multi-threading on SMP systems.
It appears not to have been updated since 2005. I don't know if there was another fork or another program being more actively maintained. It says it uses some statistics to determine how loud a file should be but is it doing it properly? Etc. etc. But yeah it appears to work OK.
Hi Brian,
how'bout gnormalize? gnormalize.sf.net
Regards,
dr_strange