Family Search has a web page devoted to the 1940 Census. They will start publishing it for free on April 2, 2012, the day the census is released by The National Archives.
FamilySearch will also provide digital images to tens of thousands of volunteers to start transcribing the records so they become searchable.
Complete publication of the index will depend on how many volunteers can help.
You can help Family Search index the 1940 Census to make it searchable sooner.