The Skinny: Garmin's Mobile PC, a software suite that provides Garmin's GPS capabilities on your laptop with any GPS receiver. It's available by itself for $59, but if you want a more integrated approach, you can buy it with the Garmin GPS 20x sensor (USB dongle) for $99. Both will be available in April. Both versions will give you free access to Garmin's online service that feeds you weather, flight status and hotel rates.
The Catch: Using a laptop as a GPS only won't get you killed if you have a passenger, or have something secure in your car to mount it with.