DropBox "A new way to sync, store, and share your files online"

Sync
Dropbox allows you to sync your files online and across your computers automatically.

2GB of online storage for free, with up to 100GB available to paying customers.
Sync files of any size or type.
Sync Windows, Mac, and Linux computers.
Automatically syncs when new files or changes are detected.

File Sharing
Sharing files is simple. It takes only a few clicks.

Shared folders allow several people to collaborate on the same files.
See other people's changes instantly.
Use your "Public" folder to link directly to files.
Control who has access to your shared folders. Kick people out and remove the shared files from their computers in the process.
Automatically create shareable online photo galleries out of regular folders.

Download
*Note: Using this link adds 250mb to your storage.