I just found this great 3 part article on Compressors by Rip Rowan called Squish This!.
If you have ever wondered about audio compressors and why recent CD’s sound the way they do read this. Here is the hype…
The most challenging tools for newcomers to the recording scene to understand are dynamics processors: compressors, expanders, noise gates and limiters. We are all familiar with tools like EQ, reverbs, choruses, flangers — even if we don’t know exactly how they work exactly we might understand what kinds of sounds they produce. Compressors are completely different animals because they work on the musical dynamics and their effects can range from undetectable to utterly bad.
A great read with a wonderful explanation of how to use the compressor plugins available in Sound Forge.