GiveWell is a nonprofit dedicated to finding outstanding giving opportunities and publishing the full details of their analysis to help donors decide where to give.
Unlike charity evaluators that focus solely on financials, assessing administrative or fundraising costs, Give Well conducts in-depth research aiming to determine how much good a given program accomplishes (in terms of lives saved, lives improved, etc.) per dollar spent. Rather than try to rate as many charities as possible, they focus on the few charities that stand out most (by their criteria) in order to find and confidently recommend the best giving opportunities possible.
For more information, visit givewell.org.