Global Outage (cooling failure and DNS) (Wikimedia Technical Blog)
If you tried going to Wikipedia anytime from ~noon today to shortly before now (6PM) you were treated to either an "unable to find server" message or a page looking like html written by a middle-schooler (luckily Google's cache option is always there to save anyone totally without access).
Anyway, long story short there was a cooling problem in a Wikimedia datacenter in Europe and they tried to route traffic to one in Florida but they messed up changing the DNS entries. And because a lot of ISPs don't follow some protocols that speedily replace the incorrect DNS entry with the right one, the guys giving you your internet connection might not have known where Wikipedia's servers are for a while.
Oh, and of course you can already read about this on Wikipedia.
(By the way yes I am using this to experiment with breaking-news reporting. And no, I'm not sure what the point is when people are more likely to find the blog I'm referencing than this one. But why not take a crack at it? Isn't that what this thing's supposed to be for? Experimenting?)