Seagate took over Samsung's hard drive business a couple of years ago, and it continues to crank out mechanical drives under the Samsung name. The latest one is the 2.5" Spinpoint M9T, which crams an impressive 2TB of storage into a case just 9.5 mm thick. The Spinpoint isn't skinny enough to match 5- and 7-mm notebook drives, but it's a fair bit thinner than competing 2TB offerings, which are 15 mm thick.
Despite its slim profile, the Spinpoint packs three 667GB platters. A 1.5TB version is also available, and both variants have 6Gbps SATA connectivity and 32MB of DRAM cache. The spindle speed is a sluggish 5,400 RPM, though. I wouldn't recommend running an OS or applications off the M9T. Secondary storage seems like a more suitable mission, ideally accompanied by a solid-state system drive.
Slender proportions make the Spinpoint M9T well suited to external applications. Seagate seems to agree, because it's deployed the Spinpoint inside a pair of Samsung Portable external drives. The M3 and P3 Portable offer USB 3.0 connectivity and, well, that's about it. They're external hard drives. What did you expect?
The M9T and its portable incarnations don't appear to be selling online just yet. It will be interesting to see how the pricing compares. WD's 2.5" Green 2TB hard drive has a $180 price tag right now, but its 2TB My Passport portable drive is available for only $140.