Here's how I recycle a flannel shirt (this one was 50 cents from a local thrift store) and turn it into a cloth diaper (Rita's Rump Pocket in this tutorial).
1) Cut sleeves off of shirt.
2) Cut collar off and cut along seam between neck and shoulder.
3) Cut front panels off from back section.
4) Sew front halves together where they were cut from back piece (to make outside piece). Or (in the case of this shirt which happened to be huge, I was able to align and sew one of the front panels on to the back after I carefully lined up the stripes. I 3-step zig-zagged them together, then zig-zagged the seam flat to the back of the diaper.
Cut out pieces; If there is a wrong and a right side, make sure that the prints are facing the right way.
5) Sew up diaper.
I'll be placing the seam on the outside of Missy so as to minimize chance of irritation.