I looked for this a while ago. The options which I found were
Aeroplanner
Airplan
Flightcalc
Load Balance
NavigaCE
Niborex
PocketFMS
SA Flightcalc
Teletype GPS
WingX
You can google for these to find out more about each one.
I was looking for one that would work on a HP4700 in the 640x480 VGA mode, and most of them can't.
Some were really pricey.
Some have flight planning features, which work great .... if you fly in the USA (a very common problem with a lot of flight planning software).
Navbox also has a pocket/pc e6b program downloadable from their
site. I have never tried this. Navbox itself was never done for pocket/pc.
Eventually I went for
Flightcalc. It works really well.
Still not properly in 640x480 though. However I don't bother using it in 640x480 as it works well in the standard res of 320x240 and clearly 640x480 is asking too much in this rather small market. The W&B feature was what I really wanted and the graph displayed (again, some of the programs don't do graphical W&B) curiously does show fine in 640x480.