YES ITS FREE!! Autodesk is providing its users with a free navigation tool!
The new tool (did I mention it's free?) allows for forward and backward navigation inside of AutoCAD. It acts much like the forward/backward navigation within a web browser.
It is like a zoom previous, but more intuitive.
I am told that this navigation tool works in AutoCAD 2008 and in AutoCAD 2009. It integrates with the ribbon in 2009, of course.
You can get this NAVIGATION TOOL at the Autodesk Labs web site. The Labs has a ton of free and up-and-coming things. Impression got a start here, as well as Inventor Light,and other add-ons.