For getting a couple of gigabytes from point A to point B, there are plenty of online options. For getting lots of gigabytes from point A to point B... well, never underestimate the bandwidth of a carryon bag full of hard drives. If you're gonna fly that drive, best to go ruggedized and improve the likelihood of all the bits arriving safely at sunny, scenic point B.
If you're in the rugged drive market, RadTech is now shipping its tough line of Impact HDD enclosures for 2.5/3.5" drives. The aluminum casings are listed for crush loads of 4000 pounds and the drives themselves are mounted on flexible bushings to improve shock resistance. The enclosures support PATA or SATA for drive connection, and on the SATA 3.5" model you can use eSATA to connect a host (in addition to the usual Firewire 4/800 and USB2 ports). The company has also updated the Drivemate USB 1" product to include an 8 GB, encryption-enabled pocket drive. Pricing and options available over yonder at RadTech's site.