I noticed today after hitting 100 posts that my rank went up from New Blood to Grunt. I tried searching for the ranking system in the FAQ section, but couldn't find anything. So I am starting this thread for everyone and over time listing the unlocked ranks.
New Blood: The rank of New Blood is for new members and members that have under -100 posts.
Grunt: Grunt is the next unlocked rank or "One Star" and is unlocked at 100 posts.
-As I said, I will continue to edit and update this thread as ranks are unlocked.
Updated as of 12/30/2010
~MegaNis