If you haven’t plugged your iPhone into your computer recently, you might want to do so. iOS 4 is now available as a free download through iTunes.

Before downloading, make sure you transfer any purchases you may have made from your phone to your computer and run a manual backup. From there, it’s an easy install. iOS 4 brings some nice new features, including the ability to multitask, which is pretty fantastic. You can also now use custom backgrounds, create folders, have up to 5x digital zoom in the camera app, and access the new mail app, which includes threading, all among the other features.

The best part of all of this is that the update is free.

Photo from fOTOGLIF