To me what stands out is not the fact that men speak up more than women do, but that women get ignored/dismissed when they do speak. I make an effort to:

• Give them attention
• Understand their point of view
• Engage in their point of view
• Not let others (men) interrupt and if they do, quickly get back to the core discussion until the speaker is satisfied/has said everything they wanted to say

Basically give your attention not to the loudest ones, but the ones that deserve it. Things like these make all people who usually don't engage in discussions more likely to engage in the future.

When dealing with small groups, I ask participants for their perspective by name. The loudest doesn't go first, and everyone gets equal-ish time. That doesn't scale to a large forum though.

It's not just a gender thing, it's also a family/culture thing. Like I just come from a family where people will talk over each other, but than I have some balkan friends who will talk over me like it's nothing (no matter the gender). What I try to do is to adjust to the situation - if someone is quieter I will let them speak out, if someone is interrupting I will also join in in a more lively way. In a group setting if I see that someone is getting talked over - I will try to refer the conversation back to them.