Sounds like you have already cut every thing. I use the Too Cool T-shirt method. Every piece cut is a multiple of 4 inches (plus seam allowances) with the largest size being 16 x 16. This way you can use the size most appropriate for the logo on the shirt. So you could have 4 x 4, 4 x 8, 4 x 12, 4 x 16, 8 x 8, 8 x 12, 8 x 16, etc. I bought the book which has a great formulat for calculating an approximate size of quilt layout - based on the number of pieces of each dimension that you have.
Then I use a graphics program to draw the appropriate number of pieces in each size (for example 4 - 8 x 8 squares, move them around. Where there are gaps - I fill in with plain t-shirt fabric saved from the shirts. By having all the pieces in incements of 4 I know that everything will fit together.