Lack of diversity in the tech industry truly saddens me. I love technology, and I want to encourage everyone else to discover how magical it is. It's a tragedy that the industry can be so hostile to some, for apparently no reason. But as a white male, I feel powerless to do anything. I can't speak for women, or for other races, or really for anyone else. I want to help fix this, but where do I begin?
You can also do a lot to signal boost. Passing along stories, links, and books is one thing. (I'll often send people to Everyday Sexism or Project Unbreakable, for example, or to particular things on the geek feminism wiki.) And if you notice non-white-male people getting shortchanged at work, do something about it. For example, I've heard a lot of women in tech tell stories of saying things in meetings and getting totally ignored. So be the person who says, "Hey, Jane's point is really interesting, and we went right by it. Jane, could you say that again, and maybe expand a little?"
And you can do things right here. Among a number of groups, Hacker News is basically seen as a wretched hive of scum and villainy. Call out bullshit. Point out the distorting effects of privilege. When people are derailing, don't let it slide.