This was a much longer post, but I hit the wrong tab in the browser and made it vanish into the ethers, so here’s a more concise (to your benefit, I suppose) take 2:
I discovered a neat trick on a recent trip to Syn-Aud-Con’s “Hums, Buzzes, and Things That Go Zap!” workshop in Salt Lake City. If you take the barcode your airline (well, Delta, anyway, can’t speak for others) sends you in your e-ticket confirmation and copy the photo into your cellphone (I’ve got a Treo, which works great for this), you can bring that photo up on the phone and hold the screen under the barcode scanner on the check-in kiosk to log in super quick.