You will need to study the new features in version 2008, such as the declarative management framework or transparent data encryption. Apart from these, your knowledge of common features (such as how to make a backup and restore it) will carry on nicely from
version 2005.
If you search for "What's new in sql server 2008", you will find plenty of articles, such as this one:
http://www.databasejournal.com/features/mssql/article.php/3691821/What146s-new-in-SQL-2008-Part-1.htm
Once you have a list of new features, you can look them up in the online documentation.
Another alternative is to purchase the self-paced training kit for 70-432. You can read the book and skip those parts that deal with features that you already know well because they match the version that existed in SQL 2005.
