One of the first ways I got into Amateur radio was building a ADS-B receiver.
For those who do not aware of what ADS-B is, Automatic dependent surveillance—broadcast (ADS–B) is a surveillance technology in which an aircraft determines its position via satellite navigation and periodically broadcasts it, enabling it to be tracked. The information can be received by air traffic control ground stations as a replacement for secondary surveillance radar, as no interrogation signal is needed from the ground. It can also be received by other aircraft to provide situational awareness and allow self-separation. (Source Wikipedia)
Using a cheap RTL-SDR Dongle, like the ones you can buy for around £15 on Amazon which are sold as Digital TV receivers, you can set up your own LIVE aircraft radar like receiver.
Combined with a piece of software called DUMP1090 can provide a local webpage showing all the received aircraft signals. Another way is to use a piece of software called PiAware from FlightAware website, which uses their own version of dump1090 but also links up with FlightAware which then uses your received signals to publish on FlightAware, it also provides you a nice website showing your statistics.
So I decided to use a Raspberry PI to run the software, as its small, cheap and low power to run it 24/7. There are many guides on installing the software so I wont go into details other than to say if you follow the step by step guide on PiAware it is easy to set up. https://flightaware.com/adsb/piaware/build
View my Live ADS-B Receiver here http://adsb.onenewham.uk:8081/
Here is a snap shot of my Stats and link to view the latest stats: https://flightaware.com/adsb/stats/user/dru5412