The American Scientific Affiliation.
I was quite dubious about them when I first heard of them, and for good reason; it is a religious organization. This seems to be compounded when I then found out that "History" counts as a science. History is nothing of the sort, and proudly so.
However, I went to a conference they had over the last few days and was quite impressed. The two main focuses of discussion at the conference were the multiverse and origins. The presenters on the former actually teach at respectable universities and conduct research on String/M-Theory. The latter was likewise boosted by the presence of respectable neuroscientists and geneticists.
The debate was as vigorous as I've seen at strictly scientific conferences, the information was very interesting (no-mind the religious aspects of the discussion; if the scientific qualities were the same, I'd have gone to this if it was Pastafarian in origin), and in general very intellectually stimulating.
Religion in general, and Christianity in specific, would certainly have a better reputation in the world if more individuals were like those of this group.
EDIT: Oh, and one of the highlights of the conference was hearing a distant relative of Edgar Allen Poe talk about Poe's book, Eureka, in which Poe suggested the Big Bang, though he had no scientific evidence for it.