Aurora Almendral provides several. She recommends asking for a discount, a tactic that often gets her around 20% off doctor's visits:
The trick is to remember that you’re making them do less work because you don’t have health insurance. They don’t have to pay an administrator for filling out insurance paperwork. They don’t have to wait for the insurance company to send a check. They don’t even have to send out a bill. When the office gives you a discount, they’re not just being nice: You’ve saved them from doing a lot of work, and deserve one.
The Dish 