(1) The general public (use by hobby programmers, for scripting,  
mentioning in blogs, boards, magazines)
(2) Start ups (people use lisp to start a business)
(3) Major corporations (companies using lisp for production software  
products, eg. ITA)

(1-2) are of interest, major corporations tend let smaller players figure  
out new technology before they adopt them.  (2) generally follows from  
(1):  People use experience gained in hobby and OSS programming to found  
their business.  So we look at (1) in more detail:

I believe the barrier to entry is too high here, and I think the major  
reason is that the lisp world is so pluralistic:  Which implementation do  
I use?  Which IDE?  Which libraries?  Where do I get what?  
(Unfortunately) people expect there to be one way to do things, i.e. they  
expect to go to lisp.org, "click here to download", double-click the  
installer, select "example-1" and first launch, click "run", and look at  
their first own weblog :-)

As a newcomer (I remember!) lisp is quite confusing:  which implementation  
to use?  Where to download?  Where is a good discussion board?  What are  
the libraries?  (Obviously I figured it out, but it took me two weeks or  
so.  I was set up with Java/Eclipse in 15 minutes).  I hear you guys cry  
out:  "But there is implementation X that does A and implementation Y that  
does B and C.  Choice is what is great about lisp!".  I know.  Now go and  
reread this paragraph.

In conclusion, I believe that the lisp boom won't come before there is a  
canonic open source implementation and a canonic repository for  
libraries.  I believe all the material is there:  SBCL would make a great  
basis, Eclipse/Cusp a newbie-friendly IDE (which already comes with a few  
libs), we have a number of great libraries, and the wholes (currently I  
see Ajax/web app and GUI) will hopefully be filled soon.

Now the question is, of course, whether this is what we want.  After  
reading c.l.l for a year, I'd say: no.  There won't be sufficient  
community support for a "one corrent solution" approach, so lisp will stay  
pluralistic and confusing.  On the other had, those who make it through  
the first two months or so are rewarded with a great system.  And, I  
think, among those that have the endurance, a lisp boom has already  
begun.  But it won't be the ruby-on-rails kind of boom.

Peter

[1] http://groovy.codehaus.org/