To get a LISP interpreter try one of these suggestions:

For Windows
You may need Winzip to install xlisp. Visit the download site to download the newest version. Some directions will be given on downloading and installing Winzip.

For xLisp on Windows, visit the ftp site
Click on Open this file from its current location.
Winzip will start after the download completes.
Click on the Extract button.
Under the Extract go to field and type in c:\xlisp.
Then click on the extract button shown.
Close winzip.

To create a shortcut on the desktop,
open up My computer and double click on the c: drive.
Double click on the xlisp folder.
Click once on Xlisp and drag it to the desktop to create a shortcut to Xlisp.

xLisp on a Mac
For a Mac version of xlisp visit the ftp site

xLisp on Linux
Every RedHat disk has Lisp on it.

Another resource.
I found out that xlispwin lacks documentation and a tutorial. However I would like you to look at this site that has everything about Lisp. --Bathula Kotibabu

Documentation.
This site contains some documentation on Lisp. I downloaded a msword document 170 pages long. --Regards, Piyush