A howto on setting up monit on an Ubuntu server. Fairly simple and straightforward. Includes basic info on customising alerts and so on.
Put simply, Puppet is a system for automating system administration tasks. It's a language to define services, nodes, dependencies, and so on. Then it handles the "realisation" or "execution" of those definitions across multiple platforms, etc.
Linux Network Care are a specialist Linux server management company. They offer remote server administration, technical support, appliance management (cPanel, Plesk, etc) and so on.
Rack Admins are a server admin company which appear to be based out of Ukraine. Their charges start from $30/hour for administration, $60/hour for consultancy.
ircmaxwell benchmarks Lighttpd versus Apache when serving static files. Results are overwhelmingly in favour of lighttpd.
DenyHosts blocks hosts after several failed login attempts. It also provides a subscription service where you can share hosts that you block, so as to block attackers before they try the first login.