How do you enhance a bad listening room's accoustics without breaking the bank? thoughts?

I am looking at a cork wall covering product to help enhance my listening room acoustics. The room is in a condo and shares duty as an "L" shaped living / dinning room. As I have neighbor's on either side I was thinking of doing the one wall where the speakers are placed and the opposite wall where I have my sitting position (The Coach!).  I was thinking the entire sitting room wall (10x8) and the speaker area (10x8) on the opposite wall. This may also have the additional bonus of helping to reduce the noise coming from my stereo into those condo's next to me?
I was wondering what people's experience has been and successful materials used as wall coverings or panels.