Bitcoin is an online currency that can be sent and received by anyone in the world, and BitListen.com is a piece of software I wrote that visualizes everyone sending money to each other. What this means is that every time anyone sends bitcoins to anyone else, a bubble appears on BitListen.com for everyone to see. The bigger the bubble, the more money was sent. If you hang out long enough you may see some pretty large bubbles, sometimes they even fill the whole screen!
BitListen was featured on National Public Radio (NPR) as part of one of their All Things Considered radio segments. It was also featured on the front page of the popular tech news source The Verge. It has over 100,000 unique visitors, and has been forked into many different spin-off projects on GitHub, including Listen To Wikipedia.
BitListen is open source and MIT licensed.