Go green and take them. I made a charity quilt out of shirts. You might want to have a look:
http://www.quiltingboard.com/t-67019-1.htm
It was a bit more work in advance b/c of the cutting to remove seams, cuffs, collars etc.. But it was FREE fabric of very good quality and I love how it turned out. To pimp it a bit, I throw in some star blocks and quilted it with a bright red thread, which made it pop.
Best of luck and enjoy :).