What is Denali?

Denali is code name of SQL Server 2011.

Here is the list of the code name of other versions of SQL Server.

In 1988, Microsoft released its first version of SQL Server. It was developed jointly by Microsoft and Sybase for the OS/2 platform.

1993 – SQL Server 4.21 for Windows NT
1995 – SQL Server 6.0, codenamed SQL95
1996 – SQL Server 6.5, codenamed Hydra
1999 – SQL Server 7.0, codenamed Sphinx
1999 – SQL Server 7.0 OLAP, codenamed Plato
2000 – SQL Server 2000 32-bit, codenamed Shiloh (version 8.0)
2003 – SQL Server 2000 64-bit, codenamed Liberty
2005 – SQL Server 2005, codenamed Yukon (version 9.0)
2008 – SQL Server 2008, codenamed Katmai (version 10.0)
2010 – SQL Server 2008 R2, Codenamed Kilimanjaro (aka KJ)
2012– SQL Server 2012, Codenamed Denali (version 11.0)