I use orphan blocks and leftover bits and pieces to piece backings together. Here are two links to photos I posted with pieced backs.
http://www.quiltingboard.com/t-77776-1.htm
http://www.quiltingboard.com/t-85150-1.htm
I also have a stash of scraps cut into 1 1/2" and 1" logs for a scrappy log cabin and another bunch of HST I am saving for a scrappy ocean waves, these are only 1 3/4" unfinished. There are tons of uses for scraps. I even started saving my teeny tiny square up cuttings and trim offs from paper peicing to stuff pet beds with and another ziploc bag full of trimmings (actually closer to shavings as many of these trims are no more then a few threads wide) I will be setting out for the birds in the spring to use in nesting material. Odd size scraps I am saving in batiks only to make crumb blocks.
I recently realized I have very few placemats so I plan on using orphan blocks and leftovers to make some placemats. You can use them for potholders too, just have to use that special batting for those.