True frugality ranges all the way from quick actions that save a few pennies to more complex activities that save dollars and to even more complex concepts that help us use/keep/invest/grow those pennies and dollars saved.
The first one is Amy Dacycyzn's "Tightwad Gazette." That series is the backbone of saving pennies every day and in many different ways. They add up; she proved that. If you don't know, read her story.
Another good classic is "Miserly Moms" by Jonni McCoy. She tells her story and shares what she discovered about saving as much as she was making in a career.
Beyond that, The Simple Dollar is a blog about money, frugality and common sense that has gone beyond just being a blog. Trent has taken it to a whole new level.
Dave Ramsey's book "The Total Money Makeover" has changed many people's financial lives completely. It's definitely worth reading for anyone.
If you're looking for inspiration, for specific tips or for a good overall look at the frugal lifestyle, these four resources will help!