Detecting Pulsars (Rotating Neutron Stars) with an RTL-SDR
rtl-sdr.com
rtl-sdr.com
Its also worth noting that they used a 30 meter dish, which is probably on the large side for amateur radio astronomy.
[1] http://www.britastro.org/radio/projects/East_AmateurPulsarDe...
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.188...
A mobile phone antenna (and power) might be well enough then.
For those punching through without investigating, "RTL-SDR is a very cheap software defined radio that uses a DVB-T TV tuner dongle based on the RTL2832U chipset." So yea... this is pretty cool.