I just published a TechRepublic gallery examining a desktop toy called the USB Cafe Pad, which is essentially a beverage warmer. I've never been much of a hot plate on my desk kind of guy, so I was skeptical about the capabilities of the Pad from the start. I prefer the more passive keep things warm technology centered on the nature abhorrent vacuum.
Unfortunately, the USB Cafe Pad failed to impress. You can get the full details from the gallery, but I'm thinking the USB port does not have enough power to run a heating element that will actually keep my precious cup of coffee warm. The thermal mug I use everyday can keep my coffee warm for hours, which means I can drink it slower, which further means I don't get to the "bouncing of the wall" stage of caffeine high any more. Am I suggesting I'm addicted to caffeine --- you are darn tootin' I am.
Next on my list of Desktop Toys is a USB powered drink chiller --- I'm betting it will have the same lack of power problem, but I'll keep an open mind about it. Maybe it will surprise me.