Beagle, one word... PocketFMS
On the PC it downloads charts, airspace structures, weather, you name it, all from the internet. You select your origin and destination, set parameters on airspaces to avoid and it even calculates the route for you. Including wind corrections, fuel burn, legal alternates, the works.
You then transfer all this info to your PDA, attach the PDA in the cockpit somewhere so that it's visible, hook it up to a GPS receiver (antenna) and go flying. If your PDA has an internet connection you don't even have to use a PC at all - although the larger screen helps a lot when you do your route planning.