Wikipedia is now blacked-out for 24 hours.
Note that at the time of writing, clicking the “Learn more” link takes you to a page that momentarily has more information, but then itself gets blacked-out. D’oh. I’m guessing they’ll fix that soon.
I’m guessing the Google Cache will get a good workout in the next 24 hours. To use it, search Google as normal; look for the Wikipedia link, and click the right button  to make the cache preview appear, then click the “Cached” link  to look at it in full size.
This was a deliberate thing for access ‘in an emergency’.