Household Products:
Xylitol - click here to learn more about this extremely dangerous human diet food product
A human artificial sweetener found in products like sugar-free gum, oral care product, mints, nicotine gum, chewable vitamins and baked goods.
Chocolate/Caffeine stimulants
The danger associated with chocolate increases with the amount and type of chocolate eaten. Milk chocolate has the least toxicity while dark and bakers chocolate the highest. In addition, small breed dogs have a higher risk than larger breeds. Small amounts of milk chocolate, especially in large dogs, typically will have no serious effect.
Grapes/Raisins
Cases of kidney failure of dogs have been linked to ingestion of large quantities of either grapes or raisins. (estimates of amounts range from 9oz to 2lbs).
Anti-freeze
Anti-freeze is attractive to most animals because of its sweet taste. Rapid treatment after ingestion is critical to limit damage and to prevent fatalities. Anti-freeze initially causes pets to "act drunk" (first 1-3 hours), then there is typically a period where they act normal (next 1-7 hours) then the pet goes into kidney failure characterized by depression, vomiting, pain , coma and death.

Household plants
Lilies – causes kidney damage
Tulip/narcissus bulbs – gastrointestinal irritation, drooling, loss of appetite, depression, seizures, and heart abnormalities.
Rhododendron/azalea – vomiting, drooling, diarrhea, weakness, depression, heart abnormalities, possible death.
Yew – Trembling, in-coordination, difficulty breathing, gastrointestinal irritation, and heart failure.

Over the Counter & Prescription Medications
Aspirin – Cats in particular, dogs at high doses. Causes gastric ulceration, muscular weakness, brain swelling, and seizures.
Tylenol, Advil, Aleve, Motrin – Toxic to both dogs and cats. Causes gastric ulceration and kidney damage.
     *** Do not give any of these medications unless specifically directed by a veterinarian.
    The most common toxicity related to ingestion of prescription medications involve allergy medications and antidepressants.
    Please call if your pet ingests any OTC or prescription medication.

Pesticides/Insecticides
OTC Flea products (click here for more info)
Organophosphates/Carbamates/Pyrethrins – used on crops and for pest control. Causes salivation, vomiting, agitation, tremors, hyper-excitability, seizures and death.

Illicit Drugs
Marijuana – depression, incoordination, diarrhea, vomiting, drooling, increased heart rate, seizures and coma
Cocaine – depression, seizures, heart abnormalities, death
Amphetamine – agitation, tremors, seizures, heart abnormalities and death