Nyko's Charge Base 360 is finally shipping, acting much like the Charge Base PS3 they released last year. The 360 version is slightly different in that it comes with two special rechargeable battery packs with contacts that charge when docked into the charge base. If the $39 is slightly too expensive, you can go the cheaper route with Nyko's Charge Station 360, which just takes in packs instead of whole controllers. Order on June 2 and you'll be able to get their black and gold model, which looks like a original Star Trek series prop. [Nyko]
I have never looked closely at the controller on the Xbox 360 (yes, I was too busy playing the ridiculous number of games), but do they not have a standard USB port for charging them like (ahem) some other platform? Rhetorical question since, well — who would want that when you can pay money to watch your controllers creating tiny new Xbox .5 controllers?