Literally, you can send a check to the U.S. government that will go toward paying down the national debt.
CNN reports that your fellow Americans sent $8 million in fiscal 2012 for that purpose. While that might sounds like a lot, CNN points out that is just 0.000007% of the $1.1 trillion accrued this year. The total national debt stands at an astounding $16 trillion.
Read the entire story on CNN.com.