1 Night w/the ThermaPAK Cooling Pad - Boing Boing

Small (13.5" X 11.5" X 0.5"), relatively lightweight (23 oz.) and reasonably-priced ($30), the pad contains "phase change material" crystals (sodium sulfate decahydrate), which melt to help absorb the heat output from a laptop batteries, then crystallize back up when they cool after use. The quilted-like surface on the laptop side also comes into play. According to the manufacturer: ThermaPAK's pad grooves channel air under the laptop, and use the second law of thermodynamics (which states that heat will tend to flow from hot areas to cold ones to reach equilibrium) to draw heat from the laptop. The company claims these pads can extend your laptop's battery life.