The folks over at Unplggd noticed an iPad app called SoftBox Pro, which attempts to turn your iPad into a softbox you can use in your photography. While the app does offer some nice options, it costs $2.99 to do something you can pretty much accomplish on your own with any tablet. Here's how.
Step One: Download Some Patterns and Sync Them to Your Tablet
Essentially all you need to use your tablet as a light source is a blank white image and display it. What SoftBox Pro offers, however, are patterns that can add some nice effects to your photos. So I made some tablet-friendly softbox images for you. All you have to do is download these images and sync them to your tablet, then display them on the screen and point them at the subject of your photo. You can also rest them beneath your photo as well.
Step Two: Add Some Colour (If You Want)
Another thing that SoftBox Pro does is allow you to add colour to these patterns. You can also do this yourself pretty easily by opening up any of these images in Photoshop (or some other image editor), adding a layer on top, and filling it with the colour you want. Once you have your colour layer, set its blending mode to Multiply and adjust that layer's opacity as desired. Now you'll be able to save out a color-tinted version of the pattern.
Obviously this is a bit more work than adjusting a few sliders on an app, so if you'd prefer not to do it yourself, have an iPad, and $US3 to spare, you can always just grab SoftBox Pro on the iTunes App Store.