I have been on for a while, and I admit I am not OMG RAVELRY!!!!!!!!!!!!!!! But it is still a good resource, especially when it comes to patterns/yarns.
You can see pictures of a pattern you like, and see other peoples projects. Like how a sweater looks on real people. You can also see all the different yarns used for that pattern. It beats scouring google to find only a few references to what you are looking for.
I am not a terrbly social person so the rest of it is kinda lost on me. I check it out maybe once or twice a week, usually if I am looking for a pattern.