Box.net has a great promotion going on for iOS users. If you create a new account, or use an existing free account, login via the iPad or iPhone app and you’ll automatically score 50GB of space for life.

The downside with Box.net is that it doesn’t have desktop syncing like DropBox does. However, you can mount your Box.net account on your desktop and manage all your files. It’s not the speediest, but it works.