rtl-sdr dongles are awesome. I piped the audio output of mine into the audio input for Ableton Live. Then I start channel hopping, record a few minutes of FM radio, then stop recording and use Ableton's slice audio feature to chop it up into a group of samples. This way I can instantly get new 'instruments' literally out of thin air!

Also one time I was browsing different frequencies and I happened to stumble upon some conversation between two strangers. Neat what you can find.