thats very old -you can find the changelog at http://support.dotnetnuke.com/project... but it only goes back to 5.0 (you can searh in gemini and get a full list if you're interested). The release schedule has some details of the older releases - http://www.dotnetnuke.com/Products/De... and you can also read Joe's blogs for the past few years (when he was release manager) to get some more detail - http://www.dotnetnuke.com/Resources/B...

 http://www.dotnetnuke.com/Resources/W... is a very useful wiki page covering items introduced in 6.0 - you can also download user manuals (see http://www.dotnetnuke.com/Resources/W... ) which cover all the capabilities.

However, IMHO the best thing to do is simply install a new version and play around - a lot has happened and the pace of change is every increasing as DotNetNuke Corporation grows in size and can take on more challenging enhancements (expect lots of social networking capabilities next year)