The "safe" (read this as normal ) charge rate is 1C for NiCad and 2 C for NiMH. What the C stands for is the capacity of the battery. IE a 650 mah NiCad you would charge at .65, a 650 mah NiMH you would charge at 1.25.

You can go over the recommended/suggested charge rate A LITTLE without damaging the battery or drastically shortening it's life.