What is the best method to test if a Pi is stable after overclocking? Primarily the CPU, but also RAM, GPU etc.
A very easy and proven way to stress the CPU is to use cpuburn, but the generall testing of stability can only be done over a long period of time. So even if you stress the RPi for x minutes, it doesn't mean your system is 100% stable all the time. I would proceed with caution and incremental steps.
Personally I run my Pi with the highest overclocking setting in raspi-config and have had no problems. But @Winkleink made a good point about the PSU, which is important if you want to have a stable overclocked system. I have mine on a USB-charger with a max. output of 2.1A.
Personally. I run Minecraft as it gives the GTU and CPU a good work out. Not very scientific but it has worked for me so far.
If you are considering overclocking then make sure you have a good reliable PSU with at least 1.5A @ 5V. The Pi should use less than 1A and other peripherals will use the rest but when over clocking there can be extra power drawn when needed.
Most problems when overclocking are down to a lack of power rather than the reliability of the Raspberry Pi.