Sorry for not giving advanced notice - it kind of snuck up on me:
http://www.dressaday.com/2009/10/international-wear-dress-day-2009-today.html I may not be wearing a dress today because I'm still wearing maternity clothes (ugh), but no one else has any excuses:
"I work in a male-dominated industry, and I don't want to look too feminine." Newsflash: I'm pretty sure they already know you're a girl. If you treat femininity as something to apologize for, so will they. Do they worry that they are "too masculine"? I'm betting not. Acting like a guy means doing whatever the hell you want whenever the hell you want until stopped by force (as far as I can tell). So if you want to seem less feminine to fit in, try that first.
Have fun!