I did a demo fest on installing SQL Server 2008 Failover Cluster on a Windows Server 2008 system a few weeks back for a user group event and the attendees requested that I post more information about how to do a slipstream of service pack in a SQL Server 2008 installation. With Windows Server 2008 R2 already released, Microsoft released KB article 955725 highlighting the need for SQL Server 2008 Service Pack 1 when installing on either Windows 7 or Windows Server 2008 R2. I wrote an article on MSSQLTips.com about it to supplement the series on installing SQL Server 2008 Failover Cluster.
This blog post came a bit late as I needed to wait for the article to be posted on the site so I can use it as a reference.