How to say "newbie" or "noob" in Chinese?
Well, while I was researching the question I may have found the answer. 

Pleco says its 菜鸟, as well as the Chinese version of Newbie on Wikipedia. 

One of the other interpretations in Pleco is idiot which may be too harsh，and another is beginner which is neutral and descriptive. But one of the definitions is indeed newbie.

I'm pretty much sure the answer would be 菜鸟, but what the heck, let's post anyway and see if something better comes up.