The Home Buyer Tax Credit part of the House Stimulus Bill was beefed up in the Senate verion of the bill. The house version provided $7,500 credit towards someone buying a new home home allowing them to use it as a tax deduction for their 2008 taxes.
The Senate version of this bill bumped that value up to $15,000 for purchase of a new home.
The downside is that if you already bought a house with the $7,500 credit, you can not get access to the other $7,500 from the new version of the bill that was passed.
You can get this credit any time in the next year, and you just have to keep the house and not sell it for at least 2 years, otherwise you will need to repay the funds the government.
For more visit this FAQ