Thought it important to name a few resources for your pet health tool box.
PetMD - they describe themselves to be in the business of pet wellmess management.
We like quite a few things about this site, but that which is most ehlpful is their symptom center. Rodent, ferret, reptile… which ever pet you have, this resource can help you identify what your pets symptoms mean for its health.
Dog First Aid - iPhone app. Cheap: $1.99 and powerful. Fairly detailed first aid reference for injuries and illnesses to your pet. Comes in really handy.