A couple more links.  For those interested in the original SICP lectures:

http://groups.csail.mit.edu/mac/classes/6.001/abelson-sussman-lectures/

… and for Doug, there's some talk about "Continuations, closures, etc." on the LispWorks forum (which appears to be down at the moment):

http://news.gmane.org/gmane.lisp.lispworks.general/

There's mention there of DLAMBDA: 

"I would posit that Doug Hoyte's DLAMBDA and the use of it to produce little state machines embodies much of what I was aiming for. Rather than standing on our heads trying to make Lisp perform stack tricks to simulate a CALL/CC -- which we almost already have with CATCH/THROW, how about translating continuation directed computations toward something akin to DLAMBDA state machines -- which BTW are also macrology magic. And these state machines may be more efficient than attempts at duplicating continuations with indefinite extent."

BC