Will be down until around 9PM Pacfic
PlayStation Network will be down all day today as Sony does some upgrading to the PlayStation Store software. The downtime started at 5:00AM Pacific, and is expected to be down until around 9:00PM Pacific.
If you signed into the PlayStation Network within the last five days however, you should be able to play games online and use apps like Netflix, Hulu, Music Unlimited during the downtime.
For those sad they won't be able to access PSN, here's a picture of a dog on top of a tortoise with dollar bills all over them because this is the Internet.