A "church-like organization that has local congregations and meets weekly to listen to talks on rationality, the latest scientific discoveries, lectures on philosophy, the state of the world, etc."?

Sounds like a Unitarian fellowship, at least the ones I know. Some may be closer to their Protestant roots, though. Of course, they also have talks on irrationality ("spirituality") and, while atheists and other rationalists are certainly welcome, aggressive promotion of any particular world-view is discouraged.