I just switched a bunch of my sites over to running on lighttpd including http://morphgnt.org/, http://leonardo.pyworks.org/ and http://www.quisition.com/.
It took me a little while to work out how to translate my ScriptAlias directives in Apache to lighttpd (hint: configure mod_alias to map the request path to the CGI script then mod_cgi to recognize files ending in certain characters as being CGI scripts)
The only problem I now have is I've killed anonymous SVN access on pyworks.org because I was previously serving it up via Apache. I'm still investigating alternatives to running Apache just for this purpose.