Buy new pillow cases if yours look like they came from the last local rummage sale - or go out and buy some big, puffy cushions if you don't have any to spare. Toss most of them in the corner that's most exposed, then put the others in a corner along the same wall. Don't put the pillows in diagonal corners - remember, it's the irregular part of the equation that's most important, and that means hard surfaces should be opposite soft ones. You can go even further with your room tuning, of course. Three small, inexpensive rugs probably will work better than one large, pricey one.
Thick ones are better than thin ones, too.
Finally, if you have an old, padded chair hidden away somewhere, stick it in the living room in an odd location. Soft objects that size can tame a lot of the audio blues.