Amazon is offering a whole slew of cases, covers, sleeves and skins for the new Kindle, including nice looking stuff from Diane von Furstenberg, Timbuk2, Belkin, BUILT, and, my favorite, LeSportsac. Who said ebooks couldn't be beautiful? [Amazon]
I'm currently using a #0 (I think) bubble-pack envelope as a sleeve (shades of MacAir!). I have purchased a Moleskin reporter-type notebook of the appropriate dimensions, and will shortly be removing most of the pages and adding Velcro. So far none of the commercial cases has grabbed me.