First things first, I've got to agree that WiFiFoFum is the best from my experience with WiFi scanning apps for Windows Mobile. I tried MiniStumbler but it wouldn't recognise the WiFi in the Windows smart phone (Palm Treo Pro) i've been been given to test. WiFiFoFum saves in all the formats I want, Google Earth (KLM), text, Wi-scan, Tom Tom POI, MemoryMap & Netstumbler (ns1) formats, which means I can fit it in with the information I've collected very easily. Not to mention it can use the GPS built into the phone which is a big plus for me, no need to carry a notebook with GPS dongle.

You can grab a copy of WiFiFoFum from the Aspecto Software website.