However, even though I was aware of the date, I've been fished in by a few other sites...
I started out by checking my daily webcomics, and went to Questionable Content, but it came up with Dinosaur Comics instead. That's a bit weird, but I figured that there was a DNS problem, and it would probably resolve itself later. After a bit more thought, it then occurred to me that this might be deliberate, so I went to Qwantz.com (home of Dinosaur Comics), and saw an xkcd comic instead. Then at xkcd.com, they have the latest issue of Questionable Content, so we've gone full circle. That's quite a fun idea (especially since I read all three comics); I don't know whether any other sites are doing something similar.
Then I got this email through from Pizza Hut:
Sadly, if you click on the link, it turns out that they won't do your washing up for you when they deliver a pizza. As with Virgle, this was just on the edge of plausibility.