Looking for something more interesting than random web vids to pass the time on a slow workday? Consider composing some brainwaves and perhaps even sharing them with fellow heads.
The Gnaural Java applet allows you to playback binaural beat sequences in a web browser - arrange your own programs using the Gnaural software or simply download example programs and load them via the java interface.
If you're looking for something a little 'flashier' - check out this visual HTML Dreammachine. Far simpler than Gnaural, it allows you to control the rate and color of basic full-window flashes.
You can get acquainted with the mental medium via this handy frequency chart listing each range's associated states of consciousness.
(Theta [4-7hz] FTW!)
http://blog.makezine.com/archive/2008/05/brainwaves_in_a_browser.html