The Seagate FreeAgent Go (classic, brown version) has a Sync function included in its software.
Maxtor-brand OneTouch 4 and OneTouch III drives (specifically, the mini) also have a Sync function in their software, but these two do not do the same thing. This article will clarify the difference between them.
Here is an explanatory graphic, with detailed, text explanation found below.
Maxtor OneTouch Sync
The OneTouch sync function performs a computer-to-computer sync. When you launch a sync with the OneTouch drive connected, the files are stored in a common folder. All files will appear on all computers to which the drive is connected, whenever connected. For best organization, the user should perform all work and changes to files on the computer, not "hosted" by the OneTouch drive, then sync to bring the files saved on the OneTouch drive to their latest, most up-to-date, version.
Then, if the user connects the drive to a second computer and performs a sync action, the files from the second computer will also be added to the common folder, and the files from the common folder that came from the first computer will be added to the second computer. Thus both computers end up with the same files, once a sync is performed once on each computer.
Note: The Sync feature will not function between systems with different operating systems, e.g. one computer with Vista and one with XP.
FreeAgent Go classic Sync
The FreeAgent Go sync function performs a computer-to-drive sync. When you launch a sync with the FreeAgent Go drive connected, the files are stored in a separate folder for each computer. The files from each computer will be added to the Go drive and kept separate. For best organization, the user would perform his/her work on the main, "home base" computer with the Go drive connected and then perform a sync to bring the files saved on the Go drive to their latest, most up-to-date, version.
Then, if the user connects the drive to a different computer, he would, ideally, work from the Go drive, rather than on that different computer. You cannot perform Folder Sync on one system, move your FreeAgent drive to a another computer and synchronize the data from the FreeAgent drive to the second computer.
These Knowledge Base articles give more detail on this process:
Note: Newer versions of FreeAgent drives, such as the XTreme, Desk, and Go, also include a sync feature, but it functions the same as that of the OneTouch sync, described in the first section of this article.