I was just reinstalling an old favourite Uplink, and it occurred that you lot might appreciate it. Basically, it's a game where you play a hacker for hire; a story gradually starts to evolve as you go. There's a demo on the website, and it's actually pretty cheap to buy.
http://www.introversion.co.uk/uplink/
Naff all sound, no fancy graphics - but it swallows hours of my time at a go