I have been making these:
http://latelyreconstructed.wordpress.com/2011/07/01/reusable-fleece-swiffer-duster-tutorial/
They use up pieces of batting that are too small to piece into a backing. They can be washed and become a bit puffier as they get washed. Sometimes I spray endust on them as our dust is SO fine! It likes to be pushed around and not picked up! (price we pay for our lovely winters, I guess!)