I would seriously advise against the majority of laptop coolers on the 360. For whatever reason, they're usually designed to suck air away from the laptop. Whilst that sucks heat away, it also suffocates the laptop and can damage it. Similar effects can happen to the Xbox, which is dependant on its ventilation holes for air intake.
If you're worried about it overheating, the first thing to do might be open it up and actually clean the insides, removing any dust you can find. I like using pressurised gas to do this (although it has been argued that pressurised gas can do more damage than good), although it's sometimes necessary to get a cloth and just wipe some bits down when the dirt is thoroughly caked and baked.
For ventilation, you can try third party fans (fit over the existing fans and take power from the power supply), although earlier ones have been known to damage the console (later ones don't). It essentially adds 3 noisy fans on top of the two already in place. Or you could try a case mod - various methods of making cooling more effective. Or do as above and use a USB port. Some also suggest removing the metal grill from the case (saying it acts as an oven). Another option is find yourself a Jasper motherboard, which produces less heat in the first place and probably has the more efficient v2 heatsinks.
Generally though, I don't think you should need to do any more than clean it out and make sure it's in an area with plenty of space to breath. Even if you do buy a fan to help it, I really wouldn't spend much money on it (as above).