Update: 532pm Eastern / 232p Pacific
Dyn sent out an update saying it resolved the second wave of attacks, but is currently working to turn away yet another round (via GameSpot).
Original Story Follows
Widespread distributed denial-of-service (DDoS) attacks have crippled numerous services, PlayStation Network and Twitter among them (via Gizmodo).
The first wave of DDoS attacks broke out across the east and west coasts of the US earlier this morning. A few companies managed to pick themselves up, only for a second and ongoing volley to bring more down.
The US Department of Homeland Security is investigating the attacks, leading pundits such as Keith Olbermann to question whether today's outages might be a warm up for a much bigger event. "Say, not to panic anybody, but what if the (attacks) today were practice for 11/8?" Olbermann tweeted.
Dyn, a web hosting firm, got hit the worst. That was by design: like poisoning a well, targeting hosting firms cripples websites they're responsible for keeping up and running.
Some of Dyn's clients include Twitter, Visa, and Netflix.