This is a nice free tool to measure the loudness of an album/track:
http://www.orban.com/meter

You can read more about the technology behind it here:
http://www.orban.com/meter/Technology.html

Measure some classic albums, some of your all time favourites. Then do the same tests for a few current major label releases. You will realize that the so called "loudness war" is a real danger to the global music culture.

(disclaimer: I don't work for Orban!)