I found 5 flour sacks at Fred's (something between Wal-Mart & Dollar General) for $4.99. I've washed & dried them, but it will be after New Years before I use them. These are plain white. They are 100% cotton & make good kitchen towels. Mine are almost 30 inch squares. I'll starch them twice, cut once before I cut them. They are made in Pakistan. They only had one pack, but I'll check back soon.

Look at Herrschner's.com.
Also, if you have an A.C. Moore near you, they have a plethora of t-shirts.

I would suggest Dharma Trading, they have blanks for dyeing so it's all white or black but the price is reasonable