<< That thing is pretty skewed, I don't know how it comes up with that stuff. >>
The top two certainly make sense for me. Secular Humanism is a subset of atheism (just as Catholicism is subset of Christianity). Secular Humanism says that we have an obligation to advance human society through deeds and actions, since our environment and ourselves are all that is - a godless universe - and only we can improve our situation. Faith in the supernatural is misplaced and a waste of human resources and effort. Pure atheism, OTOH, is simply a lack of beliefs.
The Unitarian Universalist organization, while not a true atheist organization, has no creeds or mandated faith systems...even some of their "religious leaders" claim to be nonbelievers. They view institutional religions as examples of human culture and traditions and not necessarily truisms. They celebrate Hanukah, Christmas and Kwanzaa during the month of December, for example.