From our friends at Engadget, and here.
Overclock your Mac mini to as much as 1.58GHz

So you’re feeling lucky with that new Mac mini of yours, are you? But lucky enough to pop off a couple soldered jumpers on the motherboard in order to get an extra couple hundred MHz out of the thing? Oh really? And what if the chip doesn’t take the overclock, and runs unstable, as they often do? (You might not know this, but overclocking is more of a PC thing.) Well, step right up then, Mac mini enthusiasts have sorted out how to get 1.5 and 1.58GHz out of your cute little new box—whether it wants to or not. We can’t wait for the water cooling mods.