They've been on GiveWell's list of recommended charities for 6 years now: https://www.givedirectly.org/blog-post?id=434250678224991586...
I particularly like their commitment to producing evidence on the effectiveness of direct cash transfers. They see direct cash transfers as an important benchmark against which other charities should compare.
Full disclosure: I'm one of the UK trustees.
Donate here (US, tax deductible): https://www.givedirectly.org/give-now
Donate here (UK, with Giftaid): https://www.givedirectly.org/uk
$0.91 of every $1.00 dollar ends up in the hands of the poor.