You lot are overengineering this, I think. Ross, try this, and see how much it affects things. Quick and dirty and if you have the time, resources, and desire to do something more elaborate, go for it, but: Get a couple of large, and preferably thick, blankets, and attach them to the ceiling. Tape, whatever. That is, attach one end, and let the rest hang down. Create a little 'tent', or 'booth', or whatever, for your recording area. If you still get echoes inside the recording area, take some towels, try letting them hang from above you (like the blankets, but not reaching all the way down), or maybe fix them as a layer of padding over the ceiling. Pad the wall(s) your computer is up against with towels, if necessary. I think letting towels dangle from the ceiling might attenuate enough but it's basically going to be trial and error.
Like I said, if you want to pursue some serious sound proofing, go for it, but I think this should work, use stuff you already have or can get without hassle (duct tape, blankets, towels, step ladder), and importantly, be fast. You don't necessarily need to sound proof the whole room, blankets will muffle sound waves whether they're attached to walls or hanging freely, and this way reduces the surface area you need. Covering all four walls and ceiling is going to be...well, I don't know what size the room is, aside from 'kind of small', and you probably don't need to cover ALL of it...but still, you're talking about a couple hundred square feet, easy.
If it works out, aside from fairly securely taping a few towels securely in place on the ceiling and wall, rig up a couple of frames you can attach the blankets to and stand up to form a little booth. Shove 'em up against the wall when you don't need the isolation.
Aaaand ninja'd slightly by ichthulu.