I don't even code in Lisp, but I knew the Google Flights engine would come up, because it seems to be just about the only "serious" application ever written in Lisp. And it wasn't built by Google, but their acquisition ITA, which hails from Boston and MIT's Scheme reality distortion field. (And even MIT has stopped teaching SICP in Scheme...)
Emacs, ViaWeb, Macsyma, the DS1 Remote Agent, much of the autonomous navigation software for the Mars Rover before the Pathfinder mission... And I have built a number of small-scale web applications in Common Lisp. I'm running one of them in production right now.
