http://it.toolbox.com/blogs/securitymonkey/howto-securing-a-website-with-client-ssl-certificates-11500
A wonderful article on how to setup Client SSL authentication. Includes all the openssl commands and apache config variables.
http://semlabs.co.uk/sandbox/journal/mod_rewrite_reference.html
Just what it says on the tin, very handy.
http://wpmu.org/scaling-wordpress-wpmu-buddypress-like-edublogs/
Interesting write up by James at Incsub on how they handle scale on edublogs. Some good advice although a little light on specifics, a good starting point for research.
http://codesnippets.joyent.com/posts/show/1364
Code snippet to protect .svn / .bzr / CVS directories within apache via the .htaccess file for a single site.
http://codesnippets.joyent.com/posts/show/1365
Code snippet to protect .svn / .bzr / CVS directories within apache system wide in the httpd.conf file.
http://barry.wordpress.com/2008/05/19/mod_auth_mysql-and-phpass/
A patch for mod_auth_mysql to support the new phpass format used in WordPress 2.5+. It's an apache mod.
http://www.ircmaxell.com/articles/benchmarks/lighttpd-vs.-apache---static-files.html
ircmaxwell benchmarks Lighttpd versus Apache when serving static files. Results are overwhelmingly in favour of lighttpd.