While there are many sites that provide online storage solution, most of them are limited to basic upload/downloading and sharing features. If you are looking for a comprehensive online backup and file-sharing system that allows you to sync across multiple computers, then Syncplicity could be the one you are looking for.

Syncplicity is an online storage service that aims to make backup, sync and sharing a breeze for its users. By installing the desktop client on your computer, you will be able to easily specified the folders to backup and get it sync quickly and automatically to the server and any other computers that have Syncplicity installed.