12v battery power and mega-servo conversion kits

Hey, I'm thinking of starting a real project this summer and I was looking for a few parts. The most complicated things I think I'll need to consider are the batteries and motors. For starters, I'm looking for a 12v battery that holds plenty of current. Something that could power a few windshield wiper motors for some time. Lithium cadmium looks interesting.. or I actually might end up using power tool batteries (just had the idea!)

Also, as for the motors, I think I'll use windshield wiper motors. I probably know where to get some, but really I'm looking for some kind of kit that can convert them into giant servos so I have better control. I think oddbot did a post some time ago about this, but I can't seem to dig it up :\

Thanks if you can help!