http://www.federalhousingtaxcredit.com/

It's not really a tax credit since you have to pay it back over 15 years ($500/yr) but a $7500 interest-free loan for 15 years is not a bad deal at all. This is for folks who buy their first home (as a primary residence) on or after April 9, 2008 and before July 1, 2009. You should make less than $75k for single ($150k for married couples) to be eligible.

To get this credit, you select the appropriate section on your tax return filing next year.