NiMH cells are still very popular energy source in portable media like digital cameras, clocks, various players, etc. They provide quite good energy density for reasonable price.

Charging current of NiMH cells should be about 10% of their rated hourly capacity. And charging time should not exceed 14 hours. Following charger is what it does.

This simple but effective circuit built of ATmega8 uses PWM and ADC to control the charging current. And after recommended charging time of 14 hours it simply switches off. It has a LED indicator which starts flashing green when charging is done. Charger has to be calibrated once before use. After this is done, you just need to set potentiometers handle to right position and let the charger do its work. Charger project files can be found here.