What can I use to normalize my songs?
 

I have many different songs, some are inherently loud and others quiet. Is there a way that I can make it so that they all play at the same volume level? It gets kinda irritating in my car when I turn up the volume for a quiet song, and then the next one plays at ear-drum splitting levels.

The only programs I use for my music are MP3 To Wave (to convert mp3s to wavs), Sound Forge (to cut out the blank sounds at beginning and end), Audioactive Production Studio (sometimes to encode at 128), and Exact Audio Copy (to encode at VBR).

MP3Gain is what you need.
It analyzes your mp3 files and adjusts them to have same volume.

Awesome, I'll give it a try, thanks.