Here is a fascinating resource, a site that tells you what software other sites are running. It's at:
Netcraft says about it's own site:
www.netcraft.com is running Apache/1.3.9 (Unix) mod_perl/1.20 on FreeBSD.
Some other notable sites:
www.hotmail.com is running Apache/1.3.6 (Unix) mod_ssl/2.2.8 SSLeay/0.9.0b on FreeBSD. Hotmail is owned by MS.
www.surplusdirect.com is running Microsoft-IIS/4.0 on NT4 or Windows 98 www.west-wind.com is running Microsoft-IIS/4.0 on NT4 or Windows 98 Both running Rick's Web Connection I believe.
www.levelextreme.com is running Microsoft-IIS/4.0 on NT4 or Windows 98 There's no place like home.