As long as mentioning big projects like this, I'm a fan of givewell.org. Originally they just measured various charities effectiveness, though now they also offer to operate as a (fairly transparent) pass-through. I'm sure charity navigator is pretty good too, but I have vague memories of some issues that made me prefer GiveWell... if anyone else has anything more concrete to say for or against CharityNavigator, I'd be curious to have recollection refreshed/updated.
IIRC CN relies on judging expenses, whereas GW relies on effects. So while a charity on the former might be punished for having some percentage of 'overhead', it might be rated higher by the latter because its employees are more effective because they're not doing adminstrative work themselves, but instead leave that to eg secretaries.
Yeah, that's why I presume GGP preferred GiveWell.
I also think it might be good not to be too critical in general. As in, I don't care too much about overhead for most of my purchases, so if an organisation delivers a good amount of Good, then I'm not going to worry too much about whether it's the absolute most they can do. It's not like I donate that significant a part of my income anyway.
I think we're saying the same thing. I don't care about "overhead" at all. It matters not to me how much Tim Cook gets paid or how much Apple wastes on marketing--I only care about whether the iPhone I buy is better bang for my buck than the alternatives.
It's exactly the same for charity giving. (Perhaps more so for me, since my contributions cut into my living expenses in a noticeable way.)