You Know You're A Nerd When...

[Xepher]

... you start thinking about brewing beer again, and after a few hours, are reading over sourcecode for an Atmel ATTiny25 microcontroller so you can build a thermocontrol relay for a fridge conversion. http://hackaday.com/2009/03/22/brew-fridge-thermostat/

Yeah, that's right... beer brewing has been around longer than the damn written word, but I found a way to drag source code and soldering into it! :-)

[Vithan]

I realised I was a nerd when I started playing D&D and Warhammer, then I gained level 40 geek when I started making Garrett's outfit from the Thief series....

[otrstf]

A friend invited me to a naval miniatures wargame (a hobby I abandoned after I started working in the military simulation industry full-time); and suddenly I was rooting around in my basement for figures I painted several decades ago. By the end of the week, I was enrolled in a campaign, had designed a spreadsheet to track production points, and considering writing a mod to the combat rules.