What to do with free soundproofing?

The TV station where I work is moving and I managed to salvage five 8'x4' sheets of soundproofing foam (made by a company called Domtar.)
I'm in a heavily furnished 22'x12'x6.5' basement and my speakers and listening position are in a roughly 6 foot equilateral triangle at one end. I've already dampened the first wall reflection, and I can now cover the TV screen and glass cabinent door a couple feet behind an between my (rear ported) speakers. Focus is already notably better, but what else should I try with all this stuff?
have ewe dampened the 1st-wall reflections on the ceiling?
Sedond's advice is good; you might also consider making the foam into small corner tunes-type triangles for the upper corners of the room. Be careful not to overdamp the room, however--trial and error is the best method here, but having reflective and diffusive surfaces in the right places is important too. I've heard a system in a well set-up room sound dull and almost lifeless because there were too many people in the room absorbing up the sound.