GeekTool lets you display various kinds of information on your desktop via 3 default plug-ins.
Plug-Ins: - File plugin to monitor OS X activity with /var/log/system.log, or any file that you want to follow. - Shell mode to launch custom scripts or commands like "df" to check space left on filesystems or "uptime" to monitor load on your machine. - Image mode helps you monitor bandwith usage, CPU load, memory availability on your server with tools like MRTG or RRD.