No, not an official stamp from the Postal Service. Of course, the United States government wouldn't be that cool...
California queer artist Perry Hoffman has designed this stamp to celebrate the California marriage ruling. He used online postage generator zazzle.com to produce his design. The stamps are legal US postage and 50% of sales will be donated to Equality California.
His first attempt was rejected by the Postal Service, but this version sailed through. The original design was rejected for:
"Incorporates material the primary purpose of which is to advocate or protest any particular religious, social, political, legal or moral agenda of any person or entity."
You can see the rejected version and purchase information after the jump.