> I usually try to help, but never know how far to go.
As far as you would go to help any male colleagues who were being systematically excluded or bullied. Or farther.
There are a number of resources at the Geek Feminism wiki.
http://geekfeminism.wikia.com/wiki/Resources_for_allies#Men:...
I think you might be surprised at how quickly things can change if you do speak up. An extreme example: I used to think that it was a waste of time to tell men not to rape, because obviously a rapist doesn't care about social norms. But here's the weird thing. This result is controversial, but some social scientists have found that rapists think that every man rapes. I bet that $50K sideboob guy probably thinks that every guy with money acts that way. So being vocal about social norms matters more than you would think. When someone is being an asshole to the women in the office he should be socially excluded by the men (instead of the more sadly common outcome, being celebrated for it).
Codes of conduct are similarly about stating the obvious sometimes (do we REALLY have to say that this is a safe space for everyone?) but apparently it does send a message. Because so frequently people dismiss a sexist interaction as being a problem between him and her. It should be clear it's also a problem between him and the company.
Also, one of the big ways you can affect your workplace is through hiring. Most programmers (at least those influenced by SF hacker culture) participate in hiring their peers.