Ham radio enthusiast PA3FWM constructed this impressive software defined radio, which is capable of capturing nine amateur radio bands (VLF, LF, MF, 160m, 80m, 40m, 30m, 20m, 15m) simultaneously. The system comes complete with a web-based interface that lets you control which band you would like to listen in on. The image that you see above (click for a higher-res version) shows a waterfall graph for each of the radio bands. Active transmissions show up as vertical white stripes, and you can move a small yellow filter to change the frequency that you want to listen to.
There is actually a whole community of people who run stations like this, which you can find at websdr.org. If you’re interested in amateur radio but don’t have one of your own yet, or would like to see what’s happening in other parts of the world, this could be a really fun system to play with!