Found the official links from Microsoft for both SQL Server 2008 and SQL Server 2008 R2 releases:
The SQL Server 2008 builds that were released after SQL Server 2008 was released
http://support.microsoft.com/kb/956909
--
The SQL Server 2008 builds that were released after SQL Server 2008 Service Pack 1 was released
http://support.microsoft.com/kb/970365
--
The SQL Server 2008 R2 builds that were released after SQL Server 2008 R2 was released