Servers? For Linux, Windows or Mac? Well, there's obviously Apache (http://httpd.apache.org) which is the de facto web server which has binaries for both Linux and Windows. There's also the Xitami web server (http://www.xitami.org) which also has binaries for Linux and Windows and PHP can be made to work with it as well.

If you're looking to do some home hosting and don't want the trouble of fiddling around with too many config files, then I'd recommend (based on trying this out myself!) PHP Triad (http://sourceforge.net/projects/phptriad) which will install Apache and PHP for you. That said, there is a much more up to date and (now commercial) version called Sokkit (http://www.sokkit.net/pragmacms/inde...main&cslot_1=2).

Regards,

Martyn