In my experience, sexism is not overt in the software world. I do think there is an unspoken bias against anyone who is not a white male. For all the talk of egalitarianism in Silicon Valley, this is my belief:
White men have to prove their incompetence. Everyone else has to prove their competence.
This is why I think it is important to support organizations like RailsGirls looking to educate and improve the engineering skills of those minority groups. Until this bias is truly gone, white men will continue to dominate programming unless we give those minorities special opportunities to advance.