Master/node to gather and graph "everything" on your systems using Tobi Oetiker's rrdtool. It can optionally warn your surveillance software. This software package was originally called LRRD. The project. Please see http://munin-monitoring.org/
System Stability Tester is a multi platform open source clone of SuperPI and comes with a GUI and a CLI. It can be used for CPU and RAM burning, stressing and benchmarking.