Do you want to check details on a nonprofit organization? Do you want to donate but want to make sure the organization is worthy? Are you looking for a certain kind of organization but aren't sure which one? Try GuideStar.
GuideStar is itself a nonprofit that seeks "to revolutionize philanthropy and nonprofit practice by providing information that advances transparency, enables users to make better decisions, and encourages charitable giving." You can search the site and get basic information on nearly 2 million nonprofits, such as verifying the existence of a particular organization, but if you register (which is free) you can get even more, like contact information, financial information, and IRS forms. There is even the option to subscribe to GuideStar, but unless you are doing serious research you probably won't need that much in-depth information.
GuideStar is pretty easy to navigate, but there's a how-to video if you want to watch an overview of the site.
Searching for a non-profit's name is straightforward, just type it into the searchbox. You can also type in keywords, and then at the top of the results screen you'll see a list of suggestions for related searches.
If you get too many hits, click on "Refine Your Search" to add details such as location or more keywords.
Check out the search tips for help in using the site.