Any ideas of what to do with left over carpet pieces?  

when my mom redone her carpet last yr she took the left over pieces and hot glued them around part of one of those big stiff tubes and made her cat a scratching post added a couple little dangle toys and her cat uses it everyday...took a smaller piece and cut it to line one of the outside kittys house so she could go in a little warmer place in th winter ...so maybe if you have cats? or know someone who does? heck maybe even make a mat to wipe your feet on

I agree that one can be used as a doormat. I would roll up the second piece and store it in plastic and keep it. If you ever have a bad spill/stain, large burn area or what ever, you have a replacement piece that a good carpet installer can patch in to the area.