The American Recovery and Reinvestment Act of 2009

The American Recovery and Reinvestment Act of 2009 simply extended the bonus provisions of the Economic Stimulus Act of 2008. 

http://www.amper.com/publications/2009-stimulus-package.asp
http://www.irs.gov/newsroom/article/0,,id=208318,00.html

IRS Statement
50-Percent Special Depreciation Allowance/Bonus Depreciation (Section 1201) - The new law extends the 50-percent special depreciation allowance that was available for 2008 acquisitions to acquisitions of qualifying property in 2009. This provision enables businesses to deduct half the adjusted basis of qualifying property in the year it is placed in service. The extension applies to qualifying property placed in service in 2009 (2010 for long production period property and certain transportation property).