A poll from Gallup shows that 32 percent of Americans put together a budget each month to track income and expenditures, and just 30 percent have a long-term financial plan laying out savings and investment goals. (Jul 16, 2013)

Source:

http://gallup.com/poll/162872/one-three-americans-prepare-detailed-household-budget.aspx

More about this:

http://theblaze.com/stories/2013/07/16/so-what-percentage-of-americans-actually-keep-a-budget-gallup-results-may-surprise-you/

Since Mint has 7 million users I'm guessing most people budget by spreadsheet.

Or by hand. 

or budget after the fact considering the debt articles of last week? 

Possibly:

http://pandawhale.com/post/72569/80-of-americans-are-in-debt-the-average-us-household-with-debt-carries-15762-in-credit-card-debt-and-130922-in-total-debt

After the fact isn't really budgeting though.