I have found that you need to consider more than just the hardware. You have to consider workload, operating system support, and power saving configuration. I

I have found that you need to consider more than just the hardware. You have to consider workload, operating system support, and power saving configuration. In particular, running linux on new hardware or poorly configured on older hardware will run generally run hotter as the drivers aren't tuned to use all the available power saving states. If you keep the machines workload down, run the intended OS for the hardware (or use older/highly supported hardware), and maximize all the power saving features, quality hardware (Apple, IBM, etc.) will run much cooler. Other ways to keep cool include running intense operations on a remote computer, plugging in ethernet and disabling wireless, plugging in power and removing the battery, and/or getting one of those tacky cooling pads. :-)