The importance of the evolution of the open source web server Apache cannot be exaggerated. Apart from its zillion features and many installations world wide, it helps to keep a very fundamental part of the Internet open (as opposed to closed). There are countless of HOWTO:s, FAQs, and guides for this wonderful piece of software.
One very minor information resource for Apache is the Wiki. Although I’ve been using Apache for close to ten years, I didn’t find the Wiki until today; it’s staring me in the face when I go to the Apache Foundation’s website.
Some examples of useful “articles”:
Disable Image Hot Linking
http://wiki.apache.org/httpd/DisableImageHotLinking
Canonical HostNames
http://wiki.apache.org/httpd/CanonicalHostNames
Map URIs corresponding to existing files to a handler instead
http://wiki.apache.org/httpd/RewriteVirtualHandler
Privilege separation
http://wiki.apache.org/httpd/DifferentUserIDsUsingReverseProxy
These aren’t the only useful resources for Apache of course, but there are some cute tricks on the Wiki that you may find useful.