Continental Airlines has launched a test program in Houston that allows travelers to board flights using their cell phone or personal-digital assistant instead of the usual boarding pass. If it works, the program could expand to airlines and airports nationwide. How will it work? According to USA Today [1], instead of a traditional pass, Continental Airlines (CAL) and the Transportation Security Administration will let passengers show a code the airline has sent to their cell phone or PDA. Here's more [2]:

The two-dimensional bar code, a jumble of squares and rectangles, stores the passenger's name and flight information. A TSA screener will confirm the bar code's authenticity with a handheld scanner. Passengers still need to show photo identification. The electronic boarding pass also works at airport gates.

I always email myself flight information so I can open up my email on my BlackBerry when I get up to the check-in window, so I love the idea of being able to use my cell as a boarding pass. It means one less step, right?
Source [3]