You now find the AutoCAD Release History site on Between the Lines.
You will find that AutoCAD R13 added Tooltips on the toolbars and TrueType Font Support among other things. AutoCAD 2000 added the Properties Window. AutoCAD 2002 added Associative Dimensioning. AutoCAD 2007 was the big 3D release. These are just a few things you can find if you are curious.
PS. For my take on and experience of AutoCAD I have so far AutoCAD 2004 to AutoCAD 2009 covered on my AutoCAD site.