WebVet has a page on household toxins that can cause a problem for your pet, including certain foods for humans and houseplants: http://www.webvet.com/main/article?id=1870. It lists “mushrooms” as the second item in “the top pet poisoning claims in 2008, according to pet health insurance company VPI.” No word on what kind of mushrooms or if it was due to Fido gobbling something he found on a lawn.
Many of the plants I grow and use and are not common. Maitake the Wondercat is not all that curious about strange plants, but she will eat various grasses. If your dog or cat is an indiscriminate eater, I would recommend that you keep plants and mushrooms out of reach if they are in the house. No point in finding out the hard way that something else needs to be added to the list.