I'm newly addicted to
http://navy.togetherweserved.com
It's like myspace for active, retired and navy veterans. You can look up people you used to work with. I've gotten in touch with alot of old friends.
FYI, they also have
http://marines.togetherweserved.com, no army or airforce yet, I dont know if there are plans for any or not.
If any of you navy folks out there join it, please search for me and credit me as your inviter - it gives me a longer full membership that I dont have to pay.