With SpiderOak, Files can be backed up from any device that you can read from your own PC, whether it's a local drive, USB device, network attached storage, or a virtual network drive. You can schedule backup, sync, and sharing operations independently, either at a certain time of day, automatically, or at intervals ranging from every five minutes to every two days. Then, to ensure consistency between multiple devices, you can sync any backed-up folders among the devices you choose.
Finallly, SpiderOak also works as a simple file-sharing mechanism. Essentially, you can create your own subdirectory on the SpiderOak.com Web site that has a custom "RoomKey" as part of a URL which you can mail to friends or colleagues. The "ShareRoom" doesn't maintain an access control list, but it does allow friends or colleagues to see the latest server version of a folder through any browser.
The company also has an iPhone app that provides access to your storage area, with Android, BlackBerry, and Windows Mobile versions to come.
SpiderOak offers 2 GB of free storage. After that, you'll need to purchase storage in additional increments of 100 GB for $10 per month or $100 per year.
DropBox
For a simple yet powerful approach to backup, sync, and sharing, try Dropbox. Install the free software to create a "My Dropbox" folder on your Windows, Mac, or Linux computers and on iPhone, iPad, and Android mobile devices (with BlackBerry coming soon). Dropbox will automatically sync files placed in that folder among all of your devices.
To share files, you can place files in a public sub-folder, which automatically places your files in an Internet-accessible location within the Dropbox.com domain. You can right-click on a file and send the link to others for simple sharing. A separate sharing folder works specifically with photos, which are presented in gallery format through the Dropbox Web site.
Dropbox offers 2 GB of free storage, 50 GB for $9.99 per month, and 100 GB for $19.99 per month.