You can claim the tax credit if you sign a sales contract, and close before July 1, 2009.
"First-time home buyers:
The law defines "first-time home buyer" as someone who hasn't owned a home in the three years before the purchase. If your spouse owned a home in that time frame, you're not eligible. So, those eligible can claim a tax credit for 10% of the purchase price, up to a maximum credit of $8,000. The credit is refundable, which means that if you owe less than $8,000 in taxes, you'll receive a refund for the difference. The credit is not available for home purchases that exceed $800,000."
But wait there's more...
They've sweeten the deal for existing homeowners:
"Existing homeowners. Home buyers who have lived in their current home for five out of the last eight years qualify for a tax credit of up to $6,500. The deadlines are the same as for first-time home buyers."
You can claim the tax credit if you sign a sales contract, and close before July 1, 2009.
Click: USA Today article

This is good news for a lot of people out there. We need to keep stimulating the economy!
This is great money for a buyer! If we break it down it is 4% on a 200K purchase price!