Postage stamps are fun, and whimsical. I'm collecting squares for a personal quilt. I call it "A Quilter's Quilt", and I cut 1-2 squares that are 1.25" from fabrics that I liked and used in other quilts. When I'm done I'll have squares from fabrics that I put into quilts for my boys, my nieces and nephews, my grandmother, squares from my favorite jeans or favorite shirts, etc.
I would agree with Coyote Quilts about how to do it. And for more creativity, when you begin sewing all of those little squares, sew them in 2's and that way you can keep a straight line going in a string. Snip the threads that join the sets in the string. Toss the sets in a bag and then pull out 2 sets at a time, join them, and form another string. You now have rows of 4 squares. Mix those up and stitch your blocks.