The boys at Hardware Zoom have the Zalman CM-FS6F 5.1 Surroundsound headphones.
How the hell can headphones be 5.1?!? They explain it here.
The Zalman ZM-RS6F headphones are specifically designed for this purpose
- a 5.1 (5 speakers + 1 subwoofer) 6-channel full range theatre system that
can be put on your head - for your ears only. Featuring real surround sound
field close to a complete multi-channel speaker system, and enhanced spatial
and realistic effects, the RS6F has almost every feature of a six-speaker setup,
according to Zalman.