I don't know the details myself, but it is a position shared by U.S. officials that Saudis are Al Qaeda's prime backers, though not stated officially (it was exposed by Bradley Manning's embassy cable leaks):

http://en.wikipedia.org/wiki/Saudi_Arabia%E2%80%93United_Sta...

Similarly, it is known that Saudis are the prime backers behind Hamas. Most of their money comes from religious "charities":

http://en.wikipedia.org/wiki/Hamas#Funding