Creating an online disk using Rackspace Cloud Files has the added benefit of not incurring any data transfer fees.  You can see the fee schedule for each below:

To create a new Cloud Files online disk, you will start by opening the Jungle Disk Activity Monitor.

1.  Once the Activity Monitor is open, click the CONFIGURE button. 

2.  Ensure that the ADVANCED OPTIONS checkbox is checked in the lower left.

3.  On the left menu, look for CREATE AN ONLINE DISK. 

4.  If the ONLINE DISK LOCATION is not selected as RACKSPACE CLOUD FILES, click the CHANGE link next to the right (note: this is now the default option).  You can then change the drop down to RACKSPACE CLOUD FILES and continue with the normal Online Disk creation process by creating a name in the ONLINE DISK NAME field.  You will also want to select the type of ONLINE DISK SECURITY that you desire.

5.  After hitting Next you will see the following screen letting you know that you have completed setting up the disk.  You must click FINISH here to allow the disk to actually be created.

6.  You will then see Jungle Disk prepare to create the disk, also alerting you that you cannot change the name of the disk at a later time.  To finish the creating the disk, click on Yes.

7.  Now you are done and ready to setup the disk and create your backups!