From the README:

	Coroutines can be used to implement 'cooperative multitasking' (as
	opposed to 'preemptive multitasking').  Coroutines are very
	lightweight (on Win32, they are called 'fibers'), and when combined
	with an I/O-based scheduling system, they can be used to build highly
	scalable network servers.

	Coroutines give you the best of both worlds: the efficiency of
	asynchronous state-machine programming, with the simplicity of
	threaded programming; straight-line, readable code.  And they don't
	have the overhead of preemptive threads - nearly everything happens in
	user-space.  Also, complexity is lower because you don't have to worry
	about locking access to shared state.

WWW: http://www.dotfunk.com/projects/coro/

  -Kelly
   kbyanc@posi.net