My copy and paste repository of room treatment advice.

As far as bass traps go, what are they, how do they work, and where can I get some?

This should be a FAQ :-)

This thread on AVSForums contains everything you want to know. It'll also take a week to read.

This video by fellow AVS-er Ethan does a good job of describing what to do (although his room has 39 bass traps -- you probably don't want to start there :-)

Sites selling the stuff include:
RealTraps (good quality stuff)
GIK Acoustics (less expensive stuff)
ATS Acoustics (slanted towards DIY)
Auralex (special acoustic foam instead of fiberglass)