I'm as concerned about privacy as the next person (and a lot more than many), but sometimes I think our government goes too far, such as when it waits till 72 years post facto to release federal census data. But tomorrow, at last, is the day I've been waiting for since I began genealogy work ten years ago: the release of the 1940 census.
When that happens, Ancestry.com and other organizations will go into high gear to get the images available, online, and indexed. Ancestry is a subscription service, but is making the 1940 census available for free during 2012. Until the searchable index is available, it will be necessary to go through the more laborious process of manually searching the records by Enumeration District. I plan to do that for a few of my relatives and other research interests, because I can't wait, but will put off the majority of my 1940 research until the index is available. Patience will be rewarded with a large time savings. :)
Below are some helpful 1940 sites.
Ancestry's 1940 page (or click on the Ancestry Ace image in the side panel to the right)
UPDATE: I'm also putting the National Archives 1940census.archives.gov link here, because they have all the images available, and Ancestry.com is still in the (slow) process of uploading them. I'm not sure how much good this will do, however. While I can get to the NARA site, I still haven't gotten my first image to appear. As NARA said on their Facebook page,
After waiting for 10 years for the release of the 1940 census, we know that you are frustrated with the difficulties we're experiencing on our 1940census.archives.gov site. We completely share these frustrations! Since 9 a.m. EDT (when the site went live), we've had about 22.5 million hits to the site, which works out to about 1.9 million users. Although we developed detailed plans and our testing indicated that NARA and Inflection would be able to handle the expected load,the number of visitors was huge. Thank you for your patience despite these frustrations. We're working to resolve the problem and we'll keep you updated on the situation.
And here's the FamilySearch 1940 Census link; they are also uploading the images and have a different set available so far from Ancestry's.