1) in httpd.conf or .htaccess on the directory in question.
Options Indexes
Don't have an index.html and apache does the listing for you.
2) in httpd.conf or .htaccess on the directory in question.
AddHandler cgi-script cgi
Options ExecCGI
DirectoryIndex index.cgi index.html
Will first look for index.cgi then look for index.html
Make index.cgi a little app that lists the directory and formats in your brand etc.
3) ... erm ... there are several other options but unless for very specific applications the two above will be good enough.
Gethan
<pre>
<!--#exec command="ls -l"-->
</pre>
Or assuming ls.cgi does a pretty listing
<!--#exec cgi="ls.cgi"-->
You also need in .htaccess
Options Includes
AddHandler server-parsed .html
HTH