Over on YouTube user surfrockuk shows a fun and educational use of the RTL-SDR. Every now and then astronauts will arrange a ham radio session where they will communicate with a school. An RTL-SDR can be used to listen in on at least the downlink (astronaut talking) portion of these transmissions.
The following video shows astronaut Tim Peake transmitting from the international space station (ISS) on Feburary 19th 2016. He was speaking to Oasis Academy in the UK. To receive the signal surfrockuk used an RTL-SDR with a QFH antenna. Many people have reported that other simple antennas such as discones, quartwave ground planes and even long wire antennas have been good enough to receive transmissions from the ISS too.