American Heroes' Homeownership Assistance Act of 2008 - Amends the Internal Revenue Code to allow current or former members of the Uniformed Services who perform duty in a combat zone between 2001 and 2010, or their surviving spouses, a one-time tax credit for 10% of the purchase price of a principal residence, up to $7,500. Limits such credit to residences purchased before January 1, 2011.