American Veterinary Medical Association (AVMA) - This site is a good starting pointing point to learn more about a variety of topics, including feline injection-site sarcomas and the latest subjects in veterinary medicine.

America Association of Feline Practioners The AAFP is like the AVMA for cat doctors, and has lots of good information regarding feline health

American Board of Veterinary Practioners

UC Davis School of Veterinary Medicine - One of the finest veterinary schools in the nation, and my alma mater, is just a couple of hours away.  For difficult medical cases, including cancer treatment, this is a great resource.  Contact us for a referral.  

ASPCA National Animal Poison Control Center

American Heartworm Society - Everything you've ever wanted to know about heartworm disease can  be found here, including information on local occurance.