When I was in college, I worked at the Women's Resource Center. I was friends with one of the directors and needed scholarship work hours, and they needed someone who knew desktop publishing software and someone they could give the scut work that volunteers weren't necessarily interested in. Also, the director I was friends with was trying to set me up with the other director, but that's another story. I ended up on the board of directors.
How did I, as a man, newly associated with the group, end up a board member? The short answer is that they asked. I said no, and they asked again. I said I didn't feel qualified, and they said, "There isn't anyone else who'll do it" and I gave in.
I believed then, and still do believe that the role men should take in explicitly feminist organizations is a supporting one, not a leadership one. Be there, be helpful, be visible, and be listening. I can't speak for all men (for one thing, I don't really get sports), but staying silent isn't really my strong suit. When I was on the board, I did my best, but I can't tell you how well I succeeded.
In retrospect, I wish I'd pushed back harder on the issue of being on the board. As a middle class white guy, I had been given loads of leadership training throughout my childhood even before high school. Some of it was implicit, but some of it, like the Boy Scouts, was very explicit training on public speaking, group coordination and leadership. The women who volunteered at the Women's Resource Center with me for the most part had not. Yes, I was asked, repeatedly. But I was willing to step forward because taking a leadership role was a comfortable thing for me to do. In retrospect, I was taking a place that could have been someone else's first step into a lifetime of leadership.