You should always be working under the assumption your information is insecure with such systems anyway.
In this case, things you should do include:
-If you use a common password elsewhere (which you shouldn't be) and it's associated with any info on you PSN account (same/similar username, real name, address, etc), change it ASAP.
-Keep an eye on your credit card associated with the account for fraudulent charges. You can go as far as suspending it, but I don't think it's necessary (you are not responsible for fraudulent charges anyway).
-Do NOT respond to emails that look like they're from Sony, Playstation, or even things like Blizzard/Warcraft, Netflix, etc. if they include info matching that on your PSN account requesting any personal information. Also just be careful with links in such emails (you should be anyway, kind of obvious).
Playstation put up a FAQ about this:
PlayStation® Knowledge Center | Support - PlayStation.com
They really can't bring the network back up until they're sure it's secure or it will be hacked again very quickly.
