I use this rewrite rule:
url.rewrite-once = (
"/(.*)\.(.*)" => "$0",
"/(css|files|img|js|stats)/" => "$0",
"^/([^.]+)$" => "/index.php/$1"
)
So http://example.com/index.php/controller/action may be accessed via http://example.com/controller/action
You should place the rule into lighttpd.conf.