Don't overlook the iPhone and an app called SkyCharts. Maps are
downloaded so they are local and no carrier connection is needed. GPS
shows where you are, and clicking on an airport shows it's details.
the iPhone is a whole lot more processor than the typical PDA, so
loading is fast, and you can zoom/pan, etc. with ease. cockpit
readability is good in daylight and at night, and there are a variety
of car cradles that could be modified for aircraft use. GPS should
work, even in "Airplane" mode.

Matt