The National Archives has an informational website up and running for the anticipated release of the 1940 US Census, slated for 2 April 2012. The link to the NARA site is: http://www.archives.gov/research/census/1940/
Their partner in this endeavor, Archives.com has a new website up, however it will not be live until 2 April 2012. Their website is http://1940census.archives.gov/
Indexing of the census will take a bit of time, however for most of us this will be like Christmas in April!