Ever wanted to act out your childhood dreams of being a spy? Make has a guide for building your own audio bugging device, which broadcasts an extremely low powered FM signal about 50 metres.
The basic project here requires messing around with a soldering iron, building a circuit and then tweaking all kinds of things. The end result's a tiny little transmitter that will pick up sound and broadcast it over FM.
If you've seen the Veronica Mars movie, you get how this thing works. This is a fun little project simply meant to teach you how a variety of electronics work. Head over to Make for the full guide.