Normal battery charging for NiCads and Nickel Metal Hydride batteries is about 1/10 the rated capacity of the battery. For instance, if your battery is rated at 175 mah, then a charger putting out 17.5 mah (or somewhere close to that figure) would be 1/10th, or thereabouts, the rated capacity. A charger putting out considerably more than this would be considered a "fast" charger, and a charger putting out considerably less than this would be a slow charger. Voltage-wise, for best results your charger needs to put out approximately 10% ~ 20% more than the voltage rating of the battery (although I've seen even higher outputs yet on some chargers).
Fast chargers can be nice for fast recharging, but the batteries can heat up more, and their useful life begins to deteriorate. Either have the charger on a timer, or don't forget to unplug the charger after the recommended charging time, or you will "cook" the batteries and shorten their lifespan. I've ruined perfectly good rechargeable batteries by forgetting to take them off the charger! 
Slow chargers take a lot of time to recharge obviously, but your batteries will last longer and they're not so bad about ruining the batteries if one forgets to unplug the charger after the recommended amount of charge time. Matter of fact, that's how trickle chargers work - they take a long time to recharge, and will keep your batteries topped off with virtually no affect on the batteries' life spans.
Normal charge rates (1/10 rated capacity) are kind of a middle-of-the-ground approach, balancing life span with acceptable recharge times. Trouble is, you can still "cook" your batteries with a normal charge rate if you leave it plug in too long.
I used to build and fly radio-controlled airplanes for over a decade, and rechargeable batteries were a big part of that hobby, so I learned a fair amount about rechargeable batteries during that time. 
