Howtoforge posted a guide about setting up Joomla 1.5.6 with the Lighttpd Web Server on Debian GNU/Linux 4.0

This guide explains how you can install Joomla 1.5.6 on a lighttpd web server on Debian Etch. Joomla comes with an .htaccess file with mod_rewrite rules (for Apache) (to enable search-engine friendly URLs) that do not work on lighttpd. Fortunately Joomla has a built-in method to make search-engine friendly URLs work on lighttpd as well.

Installing Joomla 1.5.6 On A Lighttpd Web Server (Debian Etch)