The website/firm you are thinking of is http://www.charitynavigator.org
Many “charities” aren’t. Even well known ones. Agreed on the United Way part. They really pissed off a lot of people. After my own research it looks to me as local church groups and the Salvation Army are about the only ones worth bothering with.
I was told that you could specify what organization you want your donation to go to with the United Way. A UW friend said, “No, if you specify, they’ll THINK about giving to that group.” Boy Scouts always seem to get left out, so UW can kiss my grits.