My hands are very sensitive to cold also and I just love my Ibex Kilometer II gloves. They'll keep my hands warm down to 40°F (sustained temperatures below that, I don't ride), but they breathe well enough that I can wear them comfortably at 60°F.

Make sure any gloves you buy fit slightly loose (it can be tough finding a pair that's just right, not so loose that you lose grip or get bunching fabric). Just like feet, even the slightest amount of pressure can cut circulation and make your hands colder.