The Register: Compaq iPaq runs Apache - "Compaq's iPaq Pocket PC has just become what's possibly the world's smallest Apache-based Web server." - http://www.theregister.co.uk/2001/01/19/compaq_ipaq_runs_apache/
Apache on VMS - MeepZor Consulting ports Apache to Open VMS/Alpha and Open VMS/VAX. - http://meepzor.com/apache-vms.html
Apache+SSL Win32 HOWTO - Setting up Apache with mod_ssl on Windows NT and 98 to provide secure HTTP services. - http://tud.at/programm/apache-ssl-win32-howto.php3
Apache Server for OS/2 - Information & utilities for running Apache Server on OS/2. Prebuilt modules for PHP3/4, and SSL. - http://silk.apana.org.au/apache/