I charge my accumulator with a constant current.
My accumulators support current constant charge.
I use a voltage regulator to provide the constant current. (look in datasheet of all classical regulator).
With this method, the circuit is simple but the charge duration is over 10 hours.
To reduce this duration you can use a fast charger (TI BQ20xx, National LM3647, MAXIM MAX712 ...), but you will pay !
The charge profile of your accumulator depends on the technology Ni-MH, Ni-Cd, Li-Ion. Have a look on battery manufacturer recommandations (SAFT, SANYO).
beuch