According to the Tax Foundation, today is "Tax Freedom Day." This means, according to the Tax Foundation, that the average American worked from January 1 until today in order to earn enough just to pay for federal, state and local taxes. For the rest of the year, the average taxpayer is earning money for herself.
For more on "Tax Freedom Day," including links to essays debating the Tax Foundation's methodology, see this TaxProfBlog post.
UPDATE: Julian Sanchez has a long explanation about why calling today "Tax Freedom Day" is misleading (even if one doesn't mischaracterize it the way I apparently did).