Martin Kirkholt Melhus's workplace bans connecting his development computer to the internet, so he hacked together a modem using HTML5: by plugging over-the-ear headphones into his laptop's 3.5mm audio jack and then placing the headphones over a network-connected built-in mic, he is able to tunnel a network connection outside the firewall (or that's the theory; as he notes, "This was only ever intended as a gimmick and a proof of concept – not something that I would actually use at work.")
The code for it is on Github.
Lately, I've been working with a client where my development computer is not connected to the Internet. This is a huge inconvenience, as the unavailability of Google and Stack Overflow vastly impact my productivity. Only recently have I begun to grasp how much of my time is actually spent copy/pasting between Visual Studio and the browser.
My office also features an Internet connected laptop and my development computer expose 3,5 mm jack sockets for audio devices. And thus my problems can be solved! Here's how I made a modem for closing the gap with Web Audio.
PS If you just want to try the modem already, head over to the live demo. Also check out the source code on github.
Web Audio Modem
A WEB-BASED MODEM