EditorSupportForLisp

You probably noticed all the parentheses. The heavy use of parentheses marks Lisp off from other languages and makes it feel unfamiliar. But once you are able to read and write the basics, it all falls together naturally. The unusual syntax of Lisp is actually the key to many of its coolest features. Matching up parentheses and indenting things properly is best handled automatically by a text editor with support for editing Lisp code, such as Vim, which can be used with Slimv --- the Superior Lisp Interaction Mode for Vim. Lots of people use the GNU Emacs text editor along with Slime, the Superior Lisp Interaction Mode for Emacs---both written in EmacsLisp.

As far as Free software goes, one of these two options---Emacs with Slime, or Vim with Slimv---is probably the best way to develop and test Lisp code. With Slime or Slimv you can edit Lisp code efficiently, send commands to the underlying Lisp environment, or redefine methods and functions in order to alter object behaviors while the system is running. (You don't get this benefit of instant updates if you don't have an editor that can communicate with your running Lisp application.) Both Emacs and Vim are highly customizable development environments, not just text editors. They're worth learning. Furthermore, Emacs and Vim are Free software, will run on basically any platform, are of very high quality, and have large, friendly user communities. That being said, you can edit Lisp code in basically any text editor, and it's quite possible that the text editor you already use has a plugin or script available for editing Lisp code and matching those parentheses. If you're unsure about Vim and Emacs, try looking around to see if you can find Lisp support for your existing editor.
 * New link: A video about using clojure with SLIMV.
 * Video about Emacs and Slime
 * Longer, more comprehensive Slime video