Available for free from the Android Market, the Southwest Airlines app can help you arrange most of your trip right from your Android device. You can check flight schedules, make reservations and check the status of your flight before you leave for the airport. Once you arrive, you can use your phone to check in wirelessly and arrange for a rental car when you land. After returning home, check the app to see how many reward points you have amassed.
The one problem with the application is that it is good for Southwest Airlines only. Still, considering the number of flights Southwest offers daily and all of the locations served, there is a good chance that you can put this app to use eventually.