I sent this short note to a local ham who's got a couple of SDR sitting in boxes unused, as a very brief introduction and some pointers to things to try that might be successful on the first go.
There's a great blog about the RTL-SDR and other digital radio stuff at
I'd poke around in there first to see what you thought might be interesting.
The very easiest thing to do on any of these is to use them as an FM tuner. Signals are very strong so it hardly matters how bad your antenna is! Depending on what system you are using you might find GQRX for Mac or Linux https://gqrx.dk/ or SDRSharp https://www.rtl-sdr.com/tag/sdrsharp/ for Windows to be useful software to control these.
Another fun exercise is to listen for airplanes, which broadcast on 1090 MHz. One of the easy ways in is to hook up the radio to a Pi and feed the data to Flightaware https://www.flightaware.com/adsb/piaware/ Even if you don't have a Pi handy, decoding ADS-B signals isn't too hard, and with good antenna placement you can decode digital signals from 100+ miles.