Sounds like it's driving you nuts like it's driving me nuts. I've been producing excessive saliva since week 6, and now in week 10, it's still going on. There seems to be no rhyme or reason as to when the saliva is more active - sometimes in the middle of the day, sometimes at night. I have to carry around tissues and napkins as well, or else you're swallowing your saliva the whole time, which causes you to intake excessive air and burp. (Which I seem to be doing more often anyway...)
My doctor reported that it is absolutely normal as well - all related to hormones of course, and there really isn't anything you *can* do about it.
For my part, I'm just REALLY hoping that this whole part of the physical symptoms will go away after a few more weeks. *crosses fingers*