Virtualisation and Failover Clustering wasn't one of the options you had for SQL Server previously, but Bob Ward has just updated a KB with details on the change of stance and why its now supported :)

In reading my blog, you'll know that I'm not the biggest fan of Virtualisation... You'll also know that its not virtualisationper se that is the issue in my view it's how the term has been percievably made into the be all and end all of issues in IT. It is still immature in my eyes as a technology to take over all other strategies in enterprise environments and people should also remember that SQL Server in itself "virtualises" on a number of different levels in its own product space namely through effective use of SQL Server instances and databases within an instance...

Take a look at the blog post in any case. Bob's posts are always great, and support of this is definitely a step in the right direction [when used for the right reasons ;) ]

http://blogs.msdn.com/psssql/archive/2009/05/19/sql-server-support-policy-for-failover-clustering-and-virtualization-gets-an-update.aspx