This page lists a number of now defunct efforts to built a modern Lisp OS. I can’t help wondering (and I’m seriously not being snarky); If Lisp is *so* damn powerful, how come all these efforts have failed?
Of course, its possible that they’ve failed because their focus is wrong. The author of the above linked to page mentions that part of the problem with building a Lisp OS is that a lot of the beginning work is low level fiddling with hardware. Maybe the Lisp community could learn something from the Smalltalk community?