Spektrum R/C Bot

Hi guys, this isnt an autonomous robot but i thought i'd post it while i wait for the rest of my "start here" parts to arrive. Its not a very complicated robot, just two GWS s03n standard servos, with an ar6200 reciever. Im using the spektrum Dx6i to control it via the ccpm config. The base is just made out of shapelock, the US version of polymorph (so i think). and i took the wheels from the old lego mindstorms kit. Theres a cap on the bottom to allow it to slide/ turn easliy. And i guess if i can add a quesiton in. For the start here robot, what recharagable battery packs work best? i really hate spending money on batteries and then seeing them thrown out so often.