I was in the middle of a customized onsite class when a client asked me if it was possible to capture the WiFi headers or packets without purchasing one of those special adapters. Of course the big qualifier was that it had to run in Windows as well.
I surprised him with Microsoft’s NetMon and showed him that you can capture the WiFi header and other WiFi Management packets.
I went on to explain that in some situations I prefer to capture packets using the native Wifi adapter and antenna that is built into the client's laptop rather than using a different adapter that would have different radio/antenna specs.
For those who haven’t played with NetMon yet, yes its free and it has some pretty unique features.