Box.net is taking advantage of the hype surrounding the iPhone 4S and iCloud by offering 50 GB of free storage to iPhone and iPad owners. The promotion is live now and will last for 50 days so you have plenty of time to sign up.
To claim your 50 GB account, you have to download the Box.net app to your iOS device and login with your account credentials. If you don't have an account, you can sign up for one on your device. Once you login, your account will be upgraded to 50 GB. These extra 50 GBs are yours to keep for as long as you have your Box.net account.