This site has the most DBTs in one site I know of:
Everything from capacitors and wire to amps, speakers, and cd players. Juicy stuff in the audio community.
Here's another dealing with amplifiers:
SBT that agrees with previous findings:
A video from Ethan Whiner that is very interesting:
Ethan's room advice:
Dr. Olive's Blog is full of great information:
Search around, it is one of the most useful sights on the web.
Everyone should really buy and read Dr. Toole's book: http://www.amazon.com/Sound-Reproduction-Acoustics-Psychoacoustics-Loudspeakers/dp/0240520092/ref=sr_1_1?ie=UTF8&s=books&qid=1239297857&sr=8-1
This will trump all the web searching you can do.