The JPL Server Monitor will check to ensure websites and server services are running and responding. It also tracks the response time of the site/service. There is a cron script that can be activated to automate the checks.
PHP-WebStatus Monitor is a script that monitors a website's connectivity. It uses php for all the scripting. It has a MySQL backend with a detailed statistics viewer.
Apache VirtualHost Transfer Counter is a set of files which allow you to quick and easy monitor utilization of http bandwitch on your server. It can give you also few statistics about VirtualHosts.