Ask HN: What are some $1B+ markets ripe for non-profits?

I am very interested in what HN thinks some $1B+ markets ripe for non-profits are? Primarily, I am wondering about software / web related ideas.<p>I work at a SaaS startup right now and have been feeling very philanthropic lately. Instead of 'volunteering' or donating, I am like the idea of building (or helping someone build) something scaleable and sustainable to help others.<p>Please HN, don't lecture. I understand: - times are hard, and so are getting donations, - nonprofit's are setup for tax reasons, - there are other ways to give back, - the charity system has contrastants, - investors, well, don't invest in NGO's, and - etc. / and more.