I am charging three alkaline AAs at the moment with a current of 65mA. I had them on charge for 4 hours last night and they have been charging for 8 hours today without getting warm. If you get one of these battery holder devices which can hold 3, 4, 6 or whatever cells in series from suppliers such as the Chinese Dealextreme.com, you can charge multiple AAs in series. This is the first time I ever tried this and my batteries are in an explosion proof box! (A butter container + scrap of thin plywood to act as a baffle!) So what if they explode, all that can happen is corrosive potassium can be blasted around the place. I am doing this outdoors in a workshop and not too worried what happens.
There is a circuit here and funny account of charging batteries here: http://www.afrotechmods.com/reallycheap/batteries/batts.htm
Sorry I meant potassium hydroxide.