There are regular requests in c.l.s and c.l.l for examples of
commercial-quality applications built with Lisp or Scheme.
In the Purdue University Mathematics Department newsletter for Summer 2005
there is a short article describing for laymen a homework-on-the-web
system I wrote using Gambit-C, a Scheme system, and Maple. I can't claim
that it's commercial (the interface isn't polished enough) but it supports
well over 2,000,000 requests from 1200 students a year, with most of these
requests coming in in the two hours before each assignment is due ;-).
(Over 40,000 per assignment in the spring semester with 800 students.)
It stays up, it takes up very little resources, I haven't lost any data,
and it is correct.
And it was built by one faculty member and two students part-time over three
years. (I remark about this because of the size of the teams the publishers
I talk to maintain in Moscow and Bangalore and Iowa and ... to develop their
own systems.)
Marc Feeley helped in crucial places to make this possible.
The link is
http://www.math.purdue.edu/about/purview/summer2005.pdf
Brad Lucier