Chatting to Pete 2E0SQL on Twitter yesterday, I was excited to hear that he had been able to decode ADSB transmissions from aircraft using his RTLSDR dongle (you'll recall that these are the devices which cost around a tenner). Although this is nothing new in the Linux world, it's new to me in the Windows world.
Even better news is that it's very simple to do.
If you already have the correct drivers from ZADIG installed, you should only need to grab the executable which is available on the SDRSHARP site
I haven't tried this myself yet, but Pete reported that he was able to decode data and plot it, using Virtual Radar Server using just a bit of coax for an antenna!
I will give this a go over the next few days - as it sounds interesting!