... I am bothered by the extreme volume variations between songs from different albums/artists. I've tried several different "volume normalization" plugins for Winamp, but none work the way I'd like. They all end up normalizing WITHIN tracks, meaning intentional volume dynamics within one song get ruined.

I think the only method that will do what you want best would be to normalize all tracks to a certain volume when you rip them from CD. Many rippers have this feature, and the option is usually a percentage (i.e., normalize to 98% of maximum). But that doesn't help you with all the encoded files you already have stored on your hard drive(s).

I don't use this myself, as I have always constantly fiddled with the volume. I find myself adjusting it all the time, even with different songs from the same album, in order to prevent certain frequencies from causing my interior paneling in the car to vibrate.