I was wondering if I could file the 401k contribution that I received last year (2008) when I file my 2009 taxes?

Any withdrawal from 401(k) is reported as income on the tax return in the year you took the withdrawal. You may also have to pay 10% early withdrawal penalty unless the withdrawal meets the requirements of an exception.
Read Your U.S. Tax Return: Elective Deferrals 401(k) Plans

Your 401K contributions are automatically deducted from your annual income on your W-2.

They are reflected on the W-2 in Box #12 with a "D" code.

More than likely, the difference between your income in Box #1 and the income reported in Box #3 and #5 will be same as the "D" code amount.