I've found something which is really fun to play with. Last time I wrote about mysterious number stations those broadcast encrypted messages anonymously using shortwave frequencies. ( To read about that and listen to some strange examples: This Way
If you love to play a spy then here is the good news. You can find number stations or amateur radio broadcasters around the world without any hardware. You don't need any big antennas or something. With help of those web softwares you can play with frequencies and try to reach some meaningful voices.
A WebSDR is a Software-Defined Radio receiver connected to the internet, allowing many listeners to listen and tune it simultaneously. SDR technology makes it possible that all listeners tune independently, and thus listen to different signals; this is in contrast to the many classical receivers that are already available via the internet.[1]
There are lots of websdr you can play with. But this one is my favourite. There is also a chatbox in which people usually send frequencies those they've found recently.
And this way to see other examples. Have fun and share your findings with us! Don't forget to comment! 馃摶
Sources:
Image and [1]: http://qrznow.com/websdr/