This is something that both Paul and I want to research more but, there have been a lot of questions about this recently. So, I thought I'd pull together a quick post of some important resources if you're interested in virtualization.
1) You should know what the support implications are – Bob Ward (Microsoft PSS Principal Escalation Engineer extraordinaire) – has blogged about the support implications here: SQL Server Support in a Hardware Virtualization Environment
2) You should know some of the best practices in configuration and setup – and the SQL team (specifically the SQLCAT team) has just recently released a whitepaper: Running SQL Server 2008 in a Hyper-V Environment – Best Practices and Performance Recommendations.
3) Finally, here are a few additional – and helpful resources:
SQL Server's virtualization section on microsoft.com: http://www.microsoft.com/sqlserver/2008/en/us/virtualization.aspx which has a lot of links/resources/references.
If you're a SQL Server Magazine subscriber, check out Demystifying SQL Server Virtualization by Mike Otey in the the September 2008 edition of SQL Server Magazine
Have fun and post back with any issues on virtualization that you've run into!