There's the Platinum Program, which is a 3% down payment grant. There's also the Mortgage Credit Certificate (MCC), which offers a first time buyer a discount on the mortgage interest paid on the loan.
Both programs are administered through the National Homebuyer's Fund. If your income does not exceed the program limits, either one or both may be good options for you. You'll want to make sure the MCC has funds available at the time of your purchase. You may be able to reserve funds.