One that I've seen reviewed is Belkin's FlyThru bag. It looks like a nice design. The laptop section unzips (not completely) so that it can 'butterfly' flat on the scanning belt. The laptop section has a clear screen so that the TSA folks won't have any question about what's inside. And I've read that the metal zippers won't interfere with the x-ray scan.
The price doesn't sound too bad ($59.99 list price, or $42.80 at the PC Connection website). I'm not sure when it will be available. PC Connection's site says to call for availability, and Circuit City says it's to be released December 8, 2008. (Anyone else nervous about buying anything from Circuit City? I believe their days as a retailer are numbered!)
Anyway, if I end up getting one, I'll update this post with an actual hands-on review of the product. If anyone else has got their hands on one, let us know what you think!