I've recently started playing with APRSIS32 and have been pleasantly surprised by how well it works, and how many features it implements...especially since it's free! It uses OpenStreetMap for to render the maps, works with any KISS TNC, and also can make use of the Kenwood radios with built in TNCs (TM-D710, TH-D72, etc.) You can do messaging, APRS email, iGate, station tracking, just about anything you want with it. If you are into APRS, it's worth downloading and trying out the software which is available at aprsisce : APRSISCE for Windows Mobile and Win32