phploadavg is a PHP script which is showing you the current web-server load as well as the history of the load for a couple of hours (configurable).
It requires a web-server (naturally) running on Linux (it uses /proc/loadavg for retrieving data) and a PHP (with sessions or PostgreSQL database) for storing the chart data (history).
Download from sourceforge: http://sourceforge.net/projects/phploadavg/
I plan to remove PostgreSQL requirement by adding support for MySQL and/or msql (requires no installation).
It would be nice to have easier configuration script. Data retrieval should be optimized to retrieve only the recent load (currently the whole chart is refreshed everytime) by AJAX.
Let me know if you know any other.