For those out there working on fighting social injustices and changing the world like we are at Pure Charity, I wanted to mention this Ruby wrapper for the Guidestar API from Mauricio Gomes of Gemini SBS.
We're making use of it :)
For example, we can...
Search by organization name:
Guidestar::Client.search(:name => "Help One Now")
Search by EIN:
Guidestar::Client.search(:ein => "26-3618295")
and more ...
From the about page:
If you care about nonprofits and the work they do, then you're affected by what GuideStar does. We gather and publicize information about nonprofit organizations. Our reach is far and wide. Our database is broad and deep. We encourage nonprofits to share information about their organizations openly and completely.
If you're new to GuideStar, you can search and find the nonprofit information you need (or integrate with their API) -
and it's free.
UPDATE: It turns out that access to the web search is free, but API access is not free. Bummer. Personally, I think a free limited API would be a smart choice for GuideStar.