Only offers 2GB free, but once you download the program on each of your computers every file you create and save to your Dropbox folder can be seen on any of your computers or compatible phone. Also you can access your files through any browser.
Dropbox allows you to sync your files online and across your computers automatically.
Work on files in your Dropbox even if you're offline. Your changes sync once your computer has an Internet connection again.
Dropbox transfers correctly resume where they left off if your connection drops.
Efficient sync: only the pieces of a file that changed (not the whole file) are synced. This saves you time.
Doesn't hog your internet connection. You can manually set bandwidth limits.
Sharing files is simple and done in only a few clicks.
See other people's changes instantly.
A Public folder that lets you link directly to files in your Dropbox.
Control who is able to access shared folders. Kick people out and remove the shared folders from their computers.
Automatically create shareable online photo galleries out of regular folders.
Dropbox backs up your files online without you having to think about it.
Automatic backup of your files.
Undelete files and folders.
Restore previous versions of your files.
30 days of undo history. Upgrades available for unlimited undo.
A copy of your files are stored on Dropbox's secure servers. This lets you access them from any computer or mobile device.
Manipulate files as you would on your desktop. Add, edit, delete, rename, etc.
A Recent Events feed that shows you a summary of activity in your Dropbox.
Security & Privacy
Dropbox takes the security and privacy of your files very seriously.
Shared folders are viewable only by people you invite.
All transmission of file data and metadata occurs over an encrypted channel (SSL).
All files stored on Dropbox servers are encrypted (AES-256).
Dropbox website and client software have been hardened against attacks from hackers.
Dropbox employees are not able to view any user's files.
Online access to your files requires your username and password.
Public files are only viewable by people who have a link to the file(s). Public folders are not browsable or searchable.
Mobile Device Access
The free application for iPhone, iPad, BlackBerry and Android lets you:
View files from within the application.
Download files for offline viewing.
Take photos and videos and sync them to your Dropbox.
Share links to files in your Dropbox.
Export your files to other applications.
Sync downloaded files so they're up-to-date.