If you live in the south you can go down to Juarez and have your dental work on the cheap. My father-in-law is fairly makes a few hundred grand per year but still does this. He likes to use it as an excuse to visit though, I guess (he's not Mexican, just likes the culture). It's very, very, very cheap. Quite clean and safe as well, despite all the negative stereotypes you hear about the country. Granted, it may depend on the clinic you visit, but there are a lot of dental practices on the border of Mexico that "specialize" in American patients right across the border. Due to laws, taxes, etc., they can offer very low prices. You can find bus services and whatnot to assist you in reaching them quite easily. Even if you're a 6 hour drive from the border, this may be a cheaper bet depending on how much work you want to do.
You can also go to a dental school. My mother is a dental hygienist. While it may sound iffy having students work on you, they are being supervised constantly.
Do you have a low income? In my town of only slightly more than 100k, we have an organization that allows low income individuals to apply for discounted rates. "Friends of Norman" in Norman, OK it is called... so it's not directly related to any practice. I believe the dentists volunteer there (or work for cheap) from various practices, but I'm not sure. You can get a root canal for 200 bucks I believe or an extraction for 40 bucks. Pretty damn cheap, really. And they'll work out a payment plan if it's necessary. You have to prove that you're low-income, though... it's not a charity for one-and-all. I'm not sure what their definition of low-income, as I referred a friend to them (like I said, I've got a dental hygienist mother, so this isn't an issue for me personally).
These three things are the only three ways of which I know to receive discounted dental care without insurance or a friendly/family connection.
