President Obama signed the American Recovery and Reinvestment Act of 2009. This act provides for a one-time payment of $250 to individuals who get Supplemental Security Income (SSI) or Social Security benefits.
The bill provided for $90,000,000 to allow Social Security to administer the cost of the $250 economic stimulus payments to Social Security beneficiaries and SSI recipients.  They look for the one-time payment to be issued no later than the first week of June 2009. DisabilityInfo.gov Benefits News & Events Update: Social Security Economic Recovery One-Time PaymentsThe one-time payment will be a separate payment that will not be included in the regular monthly benefit payment.