Jaron Deluxe Watercooling kit.

It's quite a large radiator, at 260mm by 160mm, so you'd be wise to check that you will be able to fit it inside your case.

Bringing water cooling to the masses, this kit includes nearly everything you could ask for to get the full H2O feeling. A Pondmaster 1000 pump pushes the water through the system, and is incredibly quiet while doing so. An IceCool Radiator is also included, which has mounting brackets for two 120mm fans, but unfortunately these fans aren't included in the kit. It's quite a large radiator, at 260mm by 160mm, so you'd be wise to check that you will be able to fit it inside your case. One and a half meters of Tygon hose should be more than enough pipe to rig up this kit in even the biggest of PCs.
 
The really cool stuff has to be the various water blocks included in this kit: there's a Deep Freeze CPU water block, as well as an Esky GPU water block for your video card and another Esky water block for your motherboard's Northbridge. Each is built entirely from Copper, and has a smooth and flat surface. The only problem we could find with these is the locking mechanism for the CPU water block, which is prone mounting the water block at an angle -- not the best for cooling, and at worst could leave you with a bad case of the crunchies.

Building and filling the system with water was a breeze, taking less than 20 minutes to get to a fully operational state. The hoses were quite difficult to attach to the various pieces, but in the long run you'll appreciate this as it's less likely to spring a leak. We ran the system continuously for three days and there wasn't a single bead of water leaking from it, which is reassuring.

To test this kit, we installed it on the mighty Chernobyl testing rig, with wattage set to 100W. A GlobalWin FOP-38 and the awesome Thermalright SLK-800 were tested for comparison.
 
The FOP-38 reached a scorching 81°C, while the Thermalright faired much better, peaking out at 46C. And then there was the water cooler. With a peak temperature of 38°C, it's obviously a much more efficient cooler than the two air coolers tested.

This kind of performance isn't cheap, at around $500, but it's the kind of cooler that will last for many years, with interchangeable water blocks as needed. If you can afford this sort of dosh and can overlook the imperfect CPU mount, this kit is recommended based on its ease of use and excellent performance.