Ask Slashdot: Is There a Professional Geek Dress Code?

KateKintail writes: I'm being promoted to be a director of a computer/web services department at work with staff members (not yet hired) working under me. My workplace doesn’t have a dress code 95% of the year. Is this the end of my days of jeans and enjoyably geeky t-shirts? Is there a way to dress professionally in the workplace as a boss (the kind that doesn’t need to be defeated at the end of a level) while still showing my Browncoat or Whovian love as I crawl under cobwebby desks to check that equipment is properly plugged in?