Acoustics circleRealtraps, Ethan's articles Ethan Winer: Acoustics Forumgik acousticsWhat kind of bass trap do I need? BBC/DIYMore DIYabsorption
Some links that I had lying around. There are more forums and DIY sites, but most of the forums have the same crew of experts.
I'm playing with fiberglas/diy panels, I'm treating a bad (tight) space and experimenting so that I can move on to a family space. It's well worth the effort, unfortunately I am finding the ceiling makes a really big difference in beautiful tone. Simple treatment (corners walls and ceiling err... not simple, sorry) will reward you in great bass (the holy grail).
Even my ridiculously simple attempts have yielded great results. I started off unintentionally deadening the area and learned about what worked and what took the energy away.
Otherwise take a look at some of the more respected names, it's worth the money not to have to build, and they do a better job that glued fiberglass and wood