A while back, I used this reusable swiffer duster pattern on Flickr to make a refill for my Swiffer duster out of microfiber towels. I'll admit it doesn't work quite as well as the actual dusters - they are kind of stiff, where the towel is floppy. It works well enough, and is reusable! I toss it in with my cloth diapers, since I like to use fabric softener on the rest of my laundry.
The best part is that Goose loves it, and will run around "dusting". Her technique needs a bit of work, but I figure at a minimum, I'm planting seeds for later. That reminds me, I'm due to dust again . . .
For more frugal ideas, visit Life as Mom.