Big charities tend to focus on where they can have the most impact. Smaller charities tend to focus on making an impact in a place that needs it.
My current charity work is as as Dev and Technical Consultant for a company that basically helps organizations do online evidence based mentoring and support in both urban and rural communities, using an app they developed. Founded basically by a professor to implement her research, than passed on to a new CEO when it took off. They work with a lot of Big Brothers Big Sisters chapters.
My contract runs out in Feb and I'm not sure what I'm going to do after that, given all the local layoffs. It's not like the stuff I'm working on is at Scale or uses Machine Learning or requires K8 or whatever is going to make some hiring manager's eyes light up now.