There was post a while back for Dry Mouth at night: http://oralcancersupport.org/forums/ubbthreads.php?ubb=showflat&Number=155488#Post155488

PaulB mentioned that some people use tape. I kept this in mind and then one night I used the 3M Transpore tape leftover from my hospital days. After some experimentation this is what I now do:

I put on a thin layer of lip balm on my lips. I take the tape and rip off 2 to 3 little strips. I attach the strips vertically (ala Hannibal Lector) to keep the right side of my mouth closed during sleep.

It doesn't increase saliva of course, but my mouth doesn't feel like parchment paper in the morning