Do you mean grants, as in 'free' money for first-time buyers? Or, do you simply mean loans for first-time buyers? There is very little 'free' money for first-time buyers. Most assistance consists of low-down loans from FHA or the U.S. Department of Agriculture. In some rare instances, there is downpayment assistance for income-qualified buyers. Most of these special downpayment assistance programs are handled through non-profit housing agencies. A good place to start is the Washington State Housing Finance Commission, as noted below.
Just fyi, seller's may pay closing costs for FHA and VA buyers. VA offers a zero-down loan for veterans.