NanoWeb is a PHP-based web server, and much lighter in its memory footprint than something like Apache.
It can be easily configured, basically using the nanoweb.conf file. No special configuration is required to get PHP running (confirmed for: Ubuntu Linux 10.x).
However, after following the general instructions will be necessary to modify the conf/local.php file, as DokuWiki does not automatically detect its web server location (URL).
So if your DokuWiki installation is accessible from http://yourserver.com/dokuwiki/ put the following into your local.php:
$conf['basedir'] = '/dokuwiki/'; //a trailing slash is required
Note: I encountered some performance problems with Nanoweb 2.2.9 on Ubuntu 10.04. Sometimes tendency to hang, or to respond slowly. (Quadra, 29.04.2011) Please confirm / deny!