mod_spdy, mod_pagespeed, mod rewrite cheatsheet, worker vs prefork

Varnish – reverse caching proxy

Some useful VCLs: set hit/miss header, cache adwords traffic, prevent hotlinking, serve old cache on 5xx errors, block malicious bots

Some useful tutorials

Setup fail2ban to block malicious ssh login attempts

nginx

High concurrency webserver, also very useful as a reverse caching proxy.

Cloudflare

Tough to summarize, hosted dns, reverse caching proxy with anti DoS features

Paper Trail

convenient logging of system info