Sometimes dogs just have an upset stomach that cause excess salivation, but keep a close eye on her . If she shows symptoms of tremors, lethargy, vomiting or refusal of food, she may have ingested a toxic plant or chemical as this can also cause excessive salivation. Check your yard for toxic plants or anything that might seem out of place. Dogs will also do this if they are excited or nervous or anxious. Try feeding her a bland diet of boiled chicken and rice...if she is dealing with stomach upset that will help. You can also try a dose of pepto bismol providing she is not on other medications or has a known bleeding disorder. The published dose for Pepto is 1 - 3 mg/kg DIVIDED over the course of the day. Using the middle of the range, this is the equivalent of about 1 ml/lb, but this should be divded over the course of the day, One teaspoon = 5 ml; 1 table spoon = 15 ml. But if he is on Rimadyl, please do not medicate him with anything over the counter. :)
If there is ANY swelling of the abdominal area or attempt to vomit, please see your vet immediately as it may be a problem called bloat, which is life threatening.
A small tooth abscess can also cause excessive salivation. Unfortunately, there really isn't anything you can do from home if this is the cause but do see the vet tomorrow for it. :)
I wish you all the luck and hope she feels better :)
http://www.my-dog.info/dog_diseases/poisonous_plants.asp list of common household toxic plants :)
Good luck with you boy and hope she feels better soon :)