Maxwell's Demon has been a rather popular topic, both within the circle of legitimate scientific research and, at the other end, among crackpots (no surprise there). For those not familiar with Maxwell's Demon thought experiment, there are many cites that do a very good job at explaining what it is (see here and here).
There is a very good (and lengthy) review of the physics of Maxwell's Demon in the current issue of Rev. Mod. Phys.
Abstract: Maxwell's demon was born in 1867 and still thrives in modern physics. He plays important roles in clarifying the connections between two theories: thermodynamics and information. Here the history of the demon and a variety of interesting consequences of the second law of thermodynamics are presented, mainly in quantum mechanics, but also in the theory of gravity. Also highlighted are some of the recent work that explores the role of information, illuminated by Maxwell's demon, in the arena of quantum-information theory.
The history in itself is fascinating and worth reading.
 K. Maruyama et al., Rev. Mod. Phys. v.81, p.1 (2009), or you can get the ArXiv version here.