AidGrade is a new charity evaluator that looks to be comparable to GiveWell. Their primary difference is that they *only* focus on how charities compare along particular measured outcomes (such as school attendance, birthrate, chance of opening a business, malaria), without making any effort to compare between types of charities. (This includes interesting results like "Conditional Cash Transfers and Deworming are better at improving attendance rates than scholarships")
GiveWell also does this, but designs their site to direct people towards their top charities. This is better for people with don't have the time to do the (fairly complex) work of comparing charities across domains, but AidGrade aims to be better for people that just want the raw data and the ability to form their own conclusions.
I haven't looked it enough to compare the quality of the two organizations' work, but I'm glad we finally have another organization, to encourage some competition and dialog about different approaches.
This is a fun page to play around with to get a feel for what they do:
And this is a blog post outlining their differences with GiveWell: