If you are interested in DIY acoustic treatment, I can give you some good info. Most acoustic panels are made from fibreglass. Very simply, all you need to do is buy fibreglass panels (Not the big roll up kind, but the pre-made rectangle panels.), and cover them with fabric that goes with your room. I have friends who swear that these panels are just as good as anything you can buy. I can't say for myself because I never did a comparison.
Instead of giving more details on how to make them, check this website out: http://audioperfectionist.com/. Thats the publication that I got it from. Audio Perfectionist Journal is not produced any more but their website is still up and they let you download a bunch of old issues for free. Not to get off topic, but I would encourage everyone to have a look at this web site, especially if you are new to audio. Its by far the best resource for audio equipment and setup I have ever seen.
If, for some reason, anyone has trouble downloading the Journal, just post. I'm pretty sure I still have a backup somewhere.