Sony's senior director of corporate communications and social media, Patrick Seybold, notes that it may take some time before servers are populated to the max, so don't panic if you can't access PSN immediately. The first phase of network restoration includes online play, Qriocity, video streaming, friend list functionality and PlayStation Home. The PlayStation Store is still out of commission.
Once signed in, you should be able to change your password, link that copy of Portal 2 to Steam, sync your Trophies and then sink some time into your multiplayer games. Hello, Sunday!