t-shirt quilt - GREAT TUTORIAL - best I have found so far! My sister has TONS of old shirts ! Could def. do this for her.
T-shirt quilt how-to
DIY T-shirt Quilt Pattern with Calculated Blocks: The hardest part is arranging everything to fit! Creating a pattern makes it easy to keep track of all the t-shirts, and you can customize it to make each block the color of its corresponding shirt.
T-Shirt Quilts - good idea of how many shirts it will take.