The embargo has been lifted, and for the first time, the 1940 census is not only available, but available online. The files accessible via Census.gov can be downloaded in a zip file of the whole thing or in individual PDF's. It is nicely broken down into the Census of Housing, Census of Agriculture, etc.
Here's the transcript of a pretty good NPR story (from "All Things Considered"), which you can listen to if you choose.
And here's a clip from last night's CBS nightly news.