The 1940 US census went live on April 2. There was a great deal of hub-bub leading up to the census release. There were also a number of glitches and crashes on April 2 as everyone clamoured to get online to see where their ancestors were 70 years ago.
Now that the dust has settled, but while the excitement is still alive, you can access the 1940 census for free at FamilySearch and at Ancestry.com. The free access at Ancestry is only available until April 10th.