The 2.5-inch Travelstar 5K1500 is just 9.5mm deep. Packing 1.5TB, that means the drive offers 694Gb per square inch—comfortably making it the densest HDD on the market. It draws just 1.8W, but there is one downside: it only spins at 5,400 rpm, so it's not the fastest drive you'll ever use.
Still, if your laptop's heaving under the weight of video, music and whatever else you choose to fill it up with, then this little guy could provide just the shot in the arm it needs. There's currently no pricing information, but it will be available in June. More here.