Visit the Americans for Fair Tax site right now. It's essentially a 24% national sales tax with a very high "deductible" (effectively, you don't have to pay it if you are at or below poverty level). Here's a thumbnail sketch:

The FairTax is a federal retail sales tax that replaces the entire federal income and Social Security tax systems, including personal, gift, estate, capital gains, alternative minimum, Social Security/Medicare, self-employment, and corporate taxes. The FairTax allows Americans to keep 100 percent of their paychecks (minus any state income taxes), ends corporate taxes and compliance costs hidden in the retail cost of goods and services, and fully funds the federal government while fulfilling the promise of Social Security and Medicare.

But what about the poor? They fare better under the Fair Tax than they do under the current system. Seriously. Read it and sign up.