I use Petplan.
It was $55.00/month for a rottie.
Covers ALL health problems (HD and such) and injuries. Only catch is that it cannot be a pre-exisiting condition... in other words any diagnosed illness/injury prior to insuring will not be covered, thats pretty standard with any insurance company though.
They do not cover health checkups, heart worm pills, flea & tick or any other non-injury/illness.
This insurance is great for costly health problems, there is no limitation on the cost either. I chose the $12k yearly coverage. Each year the amount resets to $12k.
More info here:
Petplan Pet Insurance for Dogs and Cats