What I've found is that our skills actually don't do much to improve the world. We're well-suited for generating economic productivity, but coding has marginal impacts on organizations whose goal is to actually help people directly in some way.
I work with them as a volunteer now, but most of what I do is help their designer debug CSS when she adds new things to the site. I did write a Salesforce integration so that a number on their site is automatically updated when people submit their contact info in a form.
But on average, I do maybe 15mins of work for them a month.
There's a few organizations which use technology directly to help people (Ashton Kutcher is involved with an organization called Thorn that uses image recognition to track down the background locations from child sexual abuse material so they can arrest the perpetrators), but most likely the best way you can help an organization is to simply do your regular "not-helping-the-world-in-any-real-way" job and donate a % of your income to people who do