Here are some links for rebate forms for Heartgard and Frontline Plus, etc that you can use to save a little of your hard earned money so you can turn around and spend it on chew toys!
If you have or plan on getting a new puppy you might also want to check with your Vet to see if they have a FREE sample of Heartgard for puppies and a NEW Puppy Kit that includes more rebate forms and a "Get Me Home" tag. Learn more about the "Get Me Home" program.
You don't have to purchase these products from your local Veterinarian, but you will need to have a valid prescription from a Vet. You can get the prescription and mail it to a Vet supply company.
Personally, I buy all my Pet meds from my local Vet as a way of helping to support my Vet. We don't have many Small Animal Vets in our area and I don't want mine going out of business because he couldn't afford to stay open. If we lost our local Vet we would have to go much further and it would cost me more in gas and time than the additional costs of the meds I buy from him.