The phenomenon of ‘binaural beats’ was first described in 1839 by Heinrich Wilhelm Dove. It is the sensation of hearing interference beats when two slightly different frequencies are played separately to each ear. The rate of the ‘perceived’ beats were claimed to modulate ones brain waves. However, little or no evidence has been brought forward since then. The few studies that seriously studied the effect could not support this claim (e.g., Owens et al., 1998), except that that it might have some effect on attention and arousal. Quite understandable, if you listen to one of the examples (see link).
The recent media attention for this phenomenon seems to be successfully bootstrapped by a new company selling mp3’s with titles like ‘Quick Hit Simulations’ describing their product with statements like ‘binaural beats will synchronize your brainwaves and help you achieve a quick hitting simulated drug simulation.’ Prices around twenty dollar. This one's for free :-)
Owens, J. et al. (1998). Binaural Auditory Beats Affect Vigilance Performance and Mood. Physiology & Behavior, 63 (2), 249-252. DOI: 10.1016/S0031-9384(97)00436-8.
Dunning, Brian. "Binaural Beats: Digital Drugs." Skeptoid Podcast. Skeptoid Media, Inc., 31 Mar 2009. Web. 31 Jul 2010.