Fract is a free, Open-source PC Benchmark based on realtime software rendering. It is designed to provide 100% unbiased results that really correspond to the raw performance of your CPU and system bus.
JCGrid is an easy-to-use tools for real-world grid-computing. It requires only to install Java Runtime and you can easy split your cpu-intensive task among several Workstations/PC/Mac/etc. It includes support for POVRay and MandelGrid as usage examples.