I never buy my towels or wash mitt from Target/Walmart/Kmart because they are made in China and are not made of pure 100% cotton or microfiber. This has been spreading in the detailing community for quite some time now so I buy my stuff from detailing supply stores. Although there's no way to prove that the towels or wash mitts are really 100%, it's better to be safe than sorry.
I use real lambs wool wash mitt and got them from eBay (
MEGUIAR'S WOOL WASH MITT *CHEAPEST ON EBAY*(GET 1 FREE): eBay Motors (item 220604688769 end time May-22-10 06:46:00 PDT))
I also use Chemical Guy's 100% cotton towel which I got from another forum.