The following are external links to other trusted websites with useful and/or fun information:
27 Ways Pets can Improve Your Health is a slide show from WebMD highlighting known benefits of owning pets.
http://www.veterinarypartner.com/ A highly reliable source of medical information for pets.
http://pets.webmd.com/default.htm Source for medical pet info from the people at WebMD.
http://www.petsandparasites.org/Companion Animal Parasite Council -- maps showing incidence of internal parasites as reported by two national laboratories. Data by state and county -- great for checking for incidence of heartworm when traveling with your pet! Also everything you always wanted to know about fleas, ticks and other pests.
The Centers for Disease Control and Prevention has excellent materials on zoonotic disease occurrence in people such as this link to parasite information http://www.cdc.gov/parasites/animals.html