I performed work in early 2009 as a contractor. I had forgotten about this work so I didn't contact where I performed the work.

I waited until February 20th to file my taxes. On March 3, I received the 1099 from this person. They were postmarked March 1st.
What do I do with this? I believe that the final date for sending these is February 28th. Since I received it after the final date, what should I do?

Well even ifyou had not received one at all, you are liable and responsible to include all of your income, so you were to include this amount in your tax filings even if you never got the 1099 at all.

So you have to now file an admended tax filing

You were required to report the income even if you did not receive 1099-misc.
You must file amended tax return with schedule C and SE and pay the tax due. File on or before April 15, 2010.

1099-misc (nonemployee compensation) income: You will report your income and business related expenses on schedule C or C-EZ (Form 1040). Then you put net income (or loss) on line 12 of Form 1040. This income is subject to SE tax at 15.3% (this is shown on line 57 of Form 1040). Your U.S. Tax Return: Tax Filing by Self Employed Sole Proprietor or Independent Contractor

Amended return