Several years ago our guild did a raffle quilt from a variety of blocks that guild members made. Putting it together was kinda like doing a jigsaw puzzle, but it really turned out nicely. We made lots of filler units - half-square triangles, four patches, flying geese, checkerboards, to make everything fit together. If you want to avoid set-in seams, come up with a standard measurement, maybe 18" and make either rows or columns that size. If you stagger where the blocks are with the filler units, it won't look like rows.
Here's a photo of the finished quilt. I have others on my blog in Feb. 2010.
Andi