Sony has begun the reactivation of PlayStation Network. The process will take several hours and, in the United States will proceed on a state-by-state basis. A map has been posted on the PlayStation blog and will be updated as areas come online.
"It will take several hours to restore PSN throughout the entire country, so please keep checking back for the latest updates," Sony said in a statement, encouraging PSN account holders to download the latest firmware (3.61) and change their account passwords, "both of which are required to get online," once service resumes.
Sony also released this video, featuring Sony Computer Entertainment head Kazuo Hirai, announcing the restoration of PlayStation Network and explaining the process.
Play On – PSN Restoration Begins Now [PlayStation.blog]