I purchased PetPlan
Petplan Pet Insurance for Dogs and Cats over the internet for Oliver & Charlie. They have WONDERFUL customer service and have been great about processing claims VERY quickly. I got it primarily to cover any unexpected issue that comes up -- although they have paid for a number of small things too (i.e. baby teeth extractions).
My little Willy that I lost a few years ago had to have emergency gall bladder surgery and spent 4 nights in ICU. That quickly added up to over $8000 in vet care. I wasn't that good about having that much saved in a puppy emergency fund I have to admit, so that was hard.
I'm really happy tho with Pet Plan so far! There is another site a lot of the insurance is rated by customers
Pet Insurance Review.