It seems that Feedburner didn't send out the email this morning from the just-after-midnight blog post, so you'll likely get two posts on April 3rd. Either way, the NARA site, though running through Amazon's cloud server, is overloaded and causing great frustrations among genealogists.
NARA has the entire census online, but as already stated, the Amazon cloud is not handling the load very well this first morning.
As of this blog post, FamilySearch has Delaware available for browsing. That link will take you to their general 1940 page, so other states will show up in the same place eventually. No word yet on when the indexing will be ready to go, but it should be later today.
As posted earlier, Ancestry already has a couple of states and territories up. They have a status list of their progress, but it's not quite correct.
The New York Public Library has put the 1940 telephone directories for New York City online.
The Online Historical Directories sites may also help you with directories for other locations.
And tooting my own horn a little, you can read about the first family members I found in the census over on my personal genealogy blog.