Common Lisp aka ANSI Standard X3J13. A popular LISP dialect.

Two unique things that make Common Lisp tempting, if you can get over the funny syntax:

• The Common Lisp Object System. Common Lisp appears to be the only language in common use that has multiple dispatch.
• Macros: with these you can create and use code generators and custom control structures with little fuss.

Quote from Paul Graham's little essay What Made Lisp Different:

9. The whole language always available. There is no real distinction between read-time, compile-time, and runtime. You can compile or run code while reading, read or run code while compiling, and read or compile code at runtime.

Running code at read-time lets users reprogram Lisp's syntax; running code at compile-time is the basis of macros; compiling at runtime is the basis of Lisp's use as an extension language in programs like Emacs; and reading at runtime enables programs to communicate using s-expressions, an idea recently reinvented as XML.

Resources

• Websites

  • http://www.lispworks.com/reference/HyperSpec/Front/index.htm -- The Common Lisp !HyperSpec? (the entire CL specification)
  • http://www.cliki.net/index -- Common Lisp Wiki
  • http://www.alu.org/alu/home -- Association of Lisp Users

• Books

  • http://www.paulgraham.com/onlisp.html -- On Lisp by Paul Graham
  • http://psg.com/~dlamkins/sl/contents.html -- Successful Lisp by David Lamkins

• Implementations

  • CMUCL -- Carnegie Mellon University Common Lisp

• IRC

  • #lisp on irc.openprojects.net