I hit the following site while surfing:
http://www.securityspace.com/s_survey/data/200301/servers.html
It includes very detailed reports they gathered through their spiders as of Feb 2003... They also interactively provide historical/comparative graphs:
web srvrs by domain
market share
server details
ssl srvrs by domain
market share
server details
certs & CAs
protocols & ciphers
apache modules
tech penetration
web authoring tools
theft & upgrades
cookie usage
isp market share
dns load balancing
web bugs
firewalled IIS
web failure/growth
p3p compact policy
telephone area code
Although I know it does not include most of the Intranet sites, the IIS 5 market share is terrible. NT4/IIS4 dropped from %25 (mid 2000) to %6, IIS 5.0 increased to %18.14... IIS 5.1 & IIS 6.0 are negligable. Various versions of Apache govern as expected...
I didn't know that there are so many different web server brands either.
[edit]fixed some typos[/edit]