Very interested in your comment about a directory that aggregates sites like this -- do you think combining different causes in a page could hurt in some way? I'd be worried that with too many causes to focus on people might get distracted.
In the meantime, you might be interested in checking out watsi.org, a site that crowdfunds healthcare for people around the world. They're explicit about where each dollar goes (100% of your donation directly goes to funding care for patients).
The original post highlights Watsi as a model but also points out that certain groups in need of help might not be as amenable to having their pictures or personal info shared online (like victims of human trafficking, etc). That would create potential problems for an aggregator of humanitarian projects like this, because the decision on how much personal information to reveal is case dependent. 6degree.org's model is somewhat similar but anonymized [1], which seems to me to be necessary in this case but isn't as effective in some ways because it lacks Watsi's human element. I definitely think that variations on the Watsi-style model could lend themselves to some kind of aggregator, but it might be a challenge to integrate them in a uniform way.
In the meantime, you might be interested in checking out watsi.org, a site that crowdfunds healthcare for people around the world. They're explicit about where each dollar goes (100% of your donation directly goes to funding care for patients).