It depends on the niche as NGO's still provides a large scope.

For instance if your NGO's is a non-profit I would immediately go to: http://www.google.com/grants/ and apply for the $10,000 per month Adwords Grant.

After that I would start by reaching out to sites listed in: http://nonprofit.alltop.com/ and http://www.businessesgrow.com/2011/05/08/the-worlds-best-non... I would reach out to them with the intention of getting a post written about the non-profit in them and/or offer them a guest post to post on their websites.

I am currently, working on something that does that. We have a couple clients now and we do the full website that includes Donations, Photos, etc.

We are trying to avoid the hackernews traffic right now as we improve our product for our current customers. You can PM me on twitter for more info. https://twitter.com/cowholio4