OMG I didn't know we had a rule about that! Where is it listed? Don't quite a high percentage of charities have a religious motivation? It seems to me that even atheist libertarian types would have an interest in promoting literary freedom that subverts totalitarian states.
AFAIK, there aren't any hard and fast "rules" per se, but Phinnaeus and Rassah have generally only considered charities that the majority of donaters agree upon and those organized by religious/political groups haven't garnered much support:
This is not exactly a charity, but it is a worthy cause in my view. An
open source movie is in the works that wants to portray life in a
resource based economy and the idea of a better world for all people. I have recently persuaded them to accept bitcoin donations for their work. For those of you who are interested in donating to or following the progress of this project, I highly encourage you to check out their
sample video and take note of their current and ongoing accomplishments.
http://www.wakingupmovie.com/2011/12/bitcoin-donations/-1
I would avoid any political, religious, or ideology based charities, as they are way too divisive. This one was especially so on just this forum alone.