Useful/Recommended Programs for Overclocking

Firstly, CPU and GPU OC stuff is a bit different...

CPU monitoring: Real Temp and HWMonitor plus CPUZ for spec check
CPU stress test (stability): Intel Burn Test (Or LinX) which runs linpack and maximizes the temps. Running at the highest RAM usage possible will give a good indication of overal stability. 15-20 passes should suffice.
Prime95 is the other one I'd recommend. You can run large or small FFT which don't work the RAM much so you can focus on CPU stability if you're having an issue with Intel Burn Test, this way you'll know if it's just the RAM that needs some tweaking.
Memtest86+ is a good way of checking RAM.

For GPU, MSI Afterburner is pretty universally accepted for being an excellent tool. Many manufacturer's have their own versions for OCing GPUs but Afterburner is quite a nice easy to use tool. For monitoring I'd suggest a combination of Afterburner and GPUZ, which will give a full temp sensor readout. Afterburner shows GPU temp but in GPUZ you can usually see more like VRAM and VRM temps, which are often the limiting factor in OCing. For stability checking, either Kombustor (comes with Afterburner) or FurMark will do the trick. They greatly increase the stress over even the most demanding games, which can be a little misleading at times but it's still a great tool.

3dMark Vantage is a good benchmark tool, but not so much meant to be a stability test. You can easily check GPU and CPU OC results by running the suite. The proffessional version also adds more benchmarks for memory and HDDs I believe.