I ran across this looking for maps for my new Garmin. The site is: http://gmapair.com
They charge $32 for a year subscription.
There is also a free one at:
http://www.xmission.com/~lalley/aviation/airspaceTab.html
I have the free one on my device now and it is very usable. It shows the airspace and altitudes but does not show any frequencies.
I don't think either of them can do any goto type navigation. Next I need to find some aviation POIs.
I got the custom map feature working now. If you have a garmin Montana, Dakota, Oregon, Colorado, GPSMAP 62/78 or Edge 800 you can install custom raster maps. I added the trail map for Great Smoky Mountain National Park to mine.
There are a few steps:
I downloaded the Map from their website in PDF format.
Converted it to a JPG with Gimp (Use the same DPI as your device)
Opened it as a map overlay in Google Earth.
Scaled and rotated it to match the area in Google Earth. (Hardest part)
Saved it as a KMZ file.
The final step is to convert the image to a tiled format that the GPS can handle.
There are a few choices for this but I use G-raster. It costs $5 to register and does all the
conversion automatically.
Link to G-Raster: http://moagu.com/?page_id=155
Drop the resulting KMZ file in your CustomMaps directory on the device and you are done.
There are a few other programs that look promising for doing this. TopoFusionPro can do the
whole process without Google Earth but I had some trouble with larger maps in the demo.