It's not even almost free, but it's still a discount. This site had our heartworm medication $30 cheaper than our vet for a 6 months supply, and lower than the other sites I have been searching. They also have other pet supplies, but I was only comparing prices on the heartworm meds. In addition, your first order you will receive a $5 coupon, as well as points for every dollar you spend.
For $10 off, plus free shipping on orders over $50
Mention code: SMART671