Is this a good memory for overclock?

I also found this one:
Kingston ValueRAM 1GB DDR 333MHz CL2.5 Non-ECC

In general, Value type RAM is not good for OCing. And, your CPU and the board it is made for will likely run memory at a stock speed of DDR400. So, for OCing, you will need some memory that runs faster than DDR400.

As said above, you want to get ram that is at least 400MHz in speed if you want to overclock, its hard to find too much high-end DDR at a reasonable price though.