If you have a petsmart near you with a pet hospital, check out their insurance! My aunt had it on one of her dogs, was paying like $40 a month and it covered everything, she only had to pay her co-pay which was something like $15 per visit! She dropped the insurance once her dog was 2 and pretty much out of the woods is what she said (she has a large breed Rott./Boxer mix). Now she is thinking of getting it again beings he is now hitting his senior years. I'm not sure if their policies are the same as they were then but it is worth checking out. Here is the link to what they cover.
http://www.petsmart.com/banfield/index.shtml
here is the link to VPI
http://www.petinsurance.com/
and a third option
http://www.petshealthplan.com/