Ah, yes. Emotional/energy vampires. Here, you might find this useful: http://hubpages.com/hub/How-to-deal-with-emotional-vampires_2
My brother-in-law is like this, and everyone in my family is in universal agreement about it.<br />
A few years ago I had a one year lease on a loft in Atlanta with a woman I knew. We had been cordial before we moved in together, but I had a hard time getting along with her, because she was very selfish from day one. I picked up the book 'how to get along with people you can't stand,' but I didn't get much from it other than general platitudes. Eventually i found a book about personality types, 'Please Understand Me II' by David Keirsey, which described the 16 basic personalities that people have, and their interactions with people of other types. One of the personality types I read about described me better than I could describe myself, and another one similarly matched my roommate. These were personalities that both of us were born with, not that we couldn't make ourselves better or worse persons if we tried.<br />
Then I found another book, 'Games Personalities Play' by Eve Delunas, which described what happened to specific personalities when we were angered or stressed. I learned about my hot buttons, and my roommates. While the rest of the year with my roommate wasn't a picnic, I learned a lot about how I could better get along with her, and how I could get her to get along better with me. <br />
I highly recommend both books, because you're probably not going to change a lot, and neither will that person who sucks the life out of a room. But you might learn something about why, and what you can do about it.
They are energy vampires