I already wrote a really long post on my own weblog on this subject, so I'll try to be brief here as an overview. If you find the idea useful and interesting you can learn more about how to apply it by reading the full post on my blog.
Basically the idea is that the only way energy vampires are a danger to you is if you decide that you need to stop them from taking your energy. If you want them to not get your energy, you have to either sheild yourself from them (which takes energy to do, so is still exhausting) or get away from them (which can be difficult in many situations and lead to a life of isolation for a really sensitive person, since most people are energy thieves at least part of the time).
Yet even for a super-empath like myself there are ways you can "feed the vampires" that actually will energize both you and them.
There are 4 key understandings necessary before this is possible: 1) you have to let go of the idea of a world of separate beings who are supposed to each get only what they have earned, be punished when they get something for nothing, and be rewarded when they somehow "earn" any joy they receive; 2) you have to also let go of the idea that the only energy available to you is that to be found within your own separate body and energy field; 3) you have to recognize that all energy is just energy. There isn't bad energy you need to be afraid of and good energy you can allow in. There's just energy; and 4) you must be willing to help people meet their needs even when they are utterly incompetent at knowing what their needs are or at pursuing them in mature, non-violent ways.
If all of this sounds like something you are willing to do... check out the full article at http://www.indigo-ocean.com and also consider picking up a copy of The Ever-Transcending Spirit by Toru Sato, which introduced me to the idea of allowing the energy theft to take place, which I had never considered before. Most of the rest of these ideas you won't find in that book (no infinite source of energy, etc.), but there are a number of other really valuable ideas that are also in the book, plus the general idea of energy exchange and ways of lifting one another up is fleshed out much, much more thoroughly, and productively so.