The new org: https://www.impactmatters.org
Not sure how it intends to differentiate from GiveWell, other than by including US charities. The description the founder gave in the NYTimes piece is clearly incorrect: [edit: This is an issue with how the NYTimes presented the quote; see comments of this post for clarification from the founder]
ImpactMatters, which is based in Manhattan, looks at how much good an organization achieves per dollar. For example, a group that provides a meal for $2 when the cost in the area is $4 will get a higher rating than a similar group that provides a meal in that area for $5.
There are already well-established charity rating systems. But Mr. Goldberg, who founded ImpactMatters with Dean Karlan, a Northwestern University economics professor who taught Mr. Goldberg at Yale, said the other ratings did not measure impact as maximizing a donor’s dollar.
GuideStar collects nonprofit groups’ tax forms, known as 990s, and makes searching for financial information easy. Charity Navigator uses the amount of money a charity spends on overhead as a crucial metric in rating a charity’s effectiveness.
GiveWell takes a more exacting approach, naming top charities based on how much good an additional dollar will do. Then there are crowdsourced sites like Great Nonprofits.