There are actually a few GPT sites out there that will actually pay you each time you clip and use a coupon. I was watching that show, too, and was wondering if any of those people use sites like that. I haven't really used those coupons, so I'm not sure how they work -- whether they'd expire quickly, have non-doubling or other specific rules that limit the amount you'd be able to save. Along with those coupons, the GPT sites sometimes also offer you a kick-back if you spend money at some store using their referral link. I've heard of some people getting some money from a GPT site for purchasing Walmart gift cards, and then clipping coupons from that site and using the gift cards to go grocery shopping at a Super Walmart store near their home.
Now I know that isn't a true Extreme Coupon tactic (as in, it isn't going to save you +90% on your grocery bills alone) but it will save you some money. And like I tell others interested in making money on-line, small drips in income make eventually make a revenue stream; likewise, using some of these coupons along with other tactics may eventually make you an extreme couponer.
You may want to check out MyPoints, InboxDollars, and SendEarnings, all of which are GPT sites similar to FC that have coupon offers that you can earn a little money back from using them (although I've gone to these sites myself, I tend to earn a lot more from the offers on FC than I do on those other sites. But they also have paid e-mails, so eventually you can earn enough to cash-out). You may also consider looking at Groupon; they tend to have coupons for +50% off on different services and restaurants. Although there may not be many other coupons you'd be able to use with the Groupon coupon, if it is a place that you frequent a lot, you'll be able to save a ton of money. I recently bought a $20 Groupon for $10 at Barnes and Nobels, and since I always go to B&N to buy my books, this was a great deal for me. I've also seen GPT sites offer you money to sign up from Groupon under them and use a Groupon!