Lisp -  (LISt Processing) - a pretty old programming language, commonly used for artificial intelligence (AI) programming.  Here some simple examples:
 

(write-line "Hello, world.") ;Print the famous greeting. ;;; A function to produce the factorial of an integer. (defun factorial (n)    (if (= n 1)      1      (* (factorial (- n 1)) n)))

Lisp was developed in 1959 by John McCarthy, it is still in wide use.
• www-formal.stanford.edu/jmc/ - John McCarthy's Home Page
• http://corman.net/CormanLisp.html - Corman Lisp - a good Common LISP for Windows Interpreter

Read those:
• www.elwoodcorp.com/alu/ - The Association of Lisp Users
• www.elwoodcorp.com/alu/table/learn.htm - Learning Lisp
• http://eksl-www.cs.umass.edu/lisp-resources/index.html - Lisp Resources
• www.cs.cmu.edu/Groups/AI/html/cltl/cltl2.html - download "Common Lisp the Language" by Guy L. Steele, 2nd ed., 1990

Here are some tutorials:
• lisp_tut.html - short lisp tutorial
• psg.com/~dlamkins/left/sl/sl.html - Successful Lisp: How to Understand and Use Common Lisp - by David B. Lamkins
  ( local_copies:  html (~500 KB) MS Word (~800KB) )
• www.cs.tulane.edu/www/Villamil/lisp/lisp1.html - tutorial
• www.apl.jhu.edu/~hall/lisp.html - Marty Hall - An Introduction and Tutorial for Common Lisp