rc-monster's online store is pretty good for lipos, chargers, etc if you want higher-end products and your budget isn't too tight.
if you want decent quality and great price, i recommend:
hobbyking.com
or
hobbypartz.com
They say a good mechanic only needs 2 tools - WD40 & Duct tape. If it moves, and its not supposed to, duct tape. If it doesn't move, and its supposed to, WD40.