The only cert that I've felt is really worth doing in the Linux admin space are the Red Hat certs and some of he more advanced CISCO certs like CCIE. In the infosec space there are two certs:"Certified Ethical Hacker" aka CEH which is as crap as it sounds, then there is OSCP - Offensive Security Certified Professional which is really difficult to get, after OSCP there is another one you can do, I can't recall the name right now. But this cert requires you to complete labs that require actual hacking so it is not your normal write an exam cert.
Regarding the CISSP cert that @netscape101 mentioned lol see this video: