MSDN has made available a SQL Server 2008 whitepaper: An Introduction to New T-SQL Programmability Features in SQL Server 2008
Summary: This paper introduces key new Transact-SQL programmability features in Microsoft SQL Server 2008 as well as SQL/Common Language Runtime (CLR) enhancements. New Transact-SQL features provide improved performance, increased functionality, and enhanced globalization support. Transact-SQL programmability enhancements in SQL Server 2008 address the needs of both OLTP and data warehouse environments.
This paper covers the following key new features
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Declaring and initializing variables
Compound assignment operators
Table value constructor support through the VALUES clause
Enhancements to the CONVERT function
New date and time data types and functions
Large UDTs
The HIERARCHYID data type
Table types and table-valued parameters
The MERGE statement, grouping sets enhancements
DDL trigger enhancements
Sparse columns
Filtered indexes
Large CLR user-defined aggregates
Multi-input CLR user-defined aggregates
The ORDER option for CLR table-valued functions
Object dependencies
Change data capture
Collation alignment with Microsoft® Windows®
Deprecation
Go to the link below and get started!
http://msdn.microsoft.com/en-gb/library/cc721270(SQL.100).aspx