Lisp never achieved widespread popularity, but it has found its way into interesting places (like the macro system for emacs), and its derivatives (such as Scheme) have popped up in interesting places as well. All the same, its influence has been on the upswing lately, as languages like C#, Ruby, and Python incorporate more and more ideas that Lisp pioneered (such as lambda calculus). Lisp is like that band that not so many people have listened to, but every band you like lists them as an influence — the Mr. Bungle of programming languages, if you will.
I have not used Lisp, but I have used Scheme, and I enjoyed the experience quite a bit. What is your experience with Lisp?
Have you used Lisp?