From Ancestry.com's main page:
At 8:30 am I'll be tuned into the National Archive's live webcast. I'll then start searching for my family on their site. But I'm also curious about how quickly other sites, such as FamilySearch and Ancestry.com will have images online. From the graphic above, it looks like Ancestry.com plans to have the first images up some time today.
I have been invited to be part of the Ancestry.com 1940 Aces program. They promise to provide updates to the progress they make in getting the census images and indexes online. I like that they're not making promises on their progress but are being realistic. They're going to do their best and they'll keep us updated.
I'm looking forward to exploring the 1940 Census... but maybe for now I should get some sleep. Only 8.5 hours to go!
Ancestry.com has select images available for American Samoa, Delaware, DC, Guam, Indiana, Maine, Nevada, Panama Canal, Rhode Island and the Virgin Islands.
FamilySearch has the complete images available for Delaware.