If you're just going to throw the thing together and leave it be, use a standard heatsink and fan...or maybe a fancy one. You get the idea.
If you're going to overclock it, mess with it, experiment, go for high benchmarks, ect. then use a liquid cooling system. It's sort of the "labor of love" idea; lot of work it, high-performance out.
Although, I do remember a story of a guy who lived in Northern Canada and had his set up so that his radiator was out his window in the snow.

He had to use antifreeze in his.