If you want to make your own washable, reusable cleaning pads for the Swiffer WetJet, you don't have to fiddle around with elastic or velcro strips to hold them into place.
I found someone blogging about how she made hers from scraps of fleece (polar fleece-- not genuine fleece, by the way ;o)), and found that they stuck to the velcro-y stuff on the Swiffer just fine (especially after being pushed around the floor a few times).
I didn't have any fleece scraps, but I did have some old, unwearable flannel pj bottoms in the rag bag, and flannel seemed at least as sticky for velcro as fleece, so I gave that a try. And yes! It works! No velcro! No elastic! Just flannel on one side and old towels (terry cloth) on the other, and it stuck perfectly.
And because (out of consideration for my readers) I believe this will conclude the saga of Swiffer, I'll conclude this entry with... "and they Swiffered happily every after (except for those times when nothing but a really thorough mopping would do the job)! The End."
Argh! Well, the first one I tried worked great. Then I used a couple more today (after publishing this post, of course), and they were less amazing... In fact, the towel side stuck to the velcro fairly well (after a little doing), but the flannel's sticking ability was less than impressive. Oh well. If all else fails, I have plenty of cheap elastic to use up.