2.4GHz parabolic mesh dishes from Chinese cookware scoops & a USB WiFi adaptor! Called "WIFRY","WOKFI" or "WOKTENNA" (12"= 300mm diam) shows 12-15dB gain (enough for a LOS range extension to 3-5km)
MIT professor Neil Gershenfeld talks about his Fab Lab -- a low-cost lab that lets people build things they need using digital and analog tools. It's a simple idea with powerful results:
Weekend Project Podcast: Make simple radios to listen too. These were made with materials that they could get their hands on and were small enough to carry around in a big pocket.