PdaNet is an application which allows “tethering” the cell data connection to a computer. This means while you are waiting for a flight at the airport you can use the internet on your laptop without paying the day pass rates as long as you have cell reception. The speed depends on whether you have 3G or EDGE, but is better than no internet and many times the same as a bogged down WiFi network.
PdaNet is free for 30 days, then there are 2 tiers: free without https support, or $23.95 for the full app which supports https. Since I often check my e-mail and other secure sites this is one application I will most likely pay for when my free trial ends. The application has worked just fine so far.
On the Backflip (and maybe other phones as well) this is a non-market app. For Backflips though this requires using special directions to install it since AT&T locked down normal ways of installing non-market apps.