Amazon S3 is quite popular these days as a file hosting service. If you use it too, CloudBerry Explorer may be the program you're looking for.
CloudBerry Explorer is an intuitive file explorer that helps you manage your Amazon S3 account just as if it was one more folder on your local drive. The program features a double-pane interface and works like an FTP client, with each window devoted to a location. These locations are not fixed and can be switched to suit your current task: local computer and remote S3 server, two local folders or even two Amazon S3 accounts.
CloudBerry Explorer supports multiple S3 accounts and lets you open multiple connections, which you can then easily manage through interface tabs. The program's configuration options also let you tweak the way the program works with files when copying and moving data.
On the downside, the program lacks some advanced functionality such as multi-thread connections for faster transfer speeds and the ability to sync folders, though according to the developer's website these are both coming soon in future versions.
CloudBerry Explorer for Amazon S3 is an efficient, intuitive file manager for your Amazon S3 accounts.
