I can relate. In the last year I have dropped two friends who were extremely self-absorbed (probably not fully NPD, in the clinical sense, but you get the idea).
One used to call me to discuss, for an hour at a time, how depressed she was that she didn't have a boyfriend or husband. (I wonder why??? hehehe) She expressed minimal interest in my life, or any subject that wasn't HER. A couple of times I experimented with discussing MY news first, and she got really agitated, like she couldn't believe she had to wait her turn.
Another friend always had a sob story, and always needed favours, but never really acted like a friend to me. Last summer she had a baby shower and did not invite me (which was okay in a way since I did not have to spend $$ for a gift), but told me about the shower afterwards - nice. Then two weeks later she calls and asks if she can come over for dinner and watch movies (with me cooking the dinner and paying for the video rental). I said no but thought to myself: Why don't you ask your baby-shower friends?
But I am well shot of them now. It's true: they NEED us, but are dead weight themselves.