The new Toshiba MK1011GAH is the world's largest capacity 1.8 inch HDD commercially available.
Toshiba uses perpendicular magnetic recording (PMR) technology and an improved error correction code to achieve an density of 240.8 megabits per square millimeter (155.3 gigabits per square inch).
The data transfer rate on the new Toshiba drive is 100MB/s, seek time is 15ms and the speed is 4,200rpm. You can see the new drive at the CES 2007.
The 100GB 1.8 inch drive measures 54x71x8mm. More details in this Toshiba press-release. Find 1.8 inch HDDs.