1)       Multi-Targeting Support

2)       Vertical Split View :

This feature show both design and source code in single window.  To enable vertical split-view orientation in VS 2008, select the tools->options menu item and go to the HTML Designer->General section.  Then check the "Split views vertically"  checkbox

3)       Javascript Debugging

Visual Studio 2008 makes it is simpler with javascript debugging. You can set break points and run the javaScript step by step and you can watch the local variables when you were debugging the javascript and solution explorer provides javascript document navigation support.

4)       Web Design and CSS Support

 Microsoft has added new Web Design and CSS Support to Visual Studio 2008

5)       AJAX & Silverlight Library support for ASP.NET

Previously developer has to install AJAX control library separately that does not come from VS, but now if you install Visual Studio 2008, you can built-in AJAX control library. Also in VS 2008 Silverlight Library is inbuilt.

6)       Access to .NET Framework Source Code

you can debug the source code of .NET Framework Library methods.

LINQ Project Overview by Don Box and Anders Hejlsberg

After two decades, the industry has reached a stable point in the evolution of object oriented programming technologies. Programmers now take for granted features like classes, objects, and methods. In looking at the current and next generation of technologies, it has become apparent that the next big challenge in programming technology is to reduce the complexity of accessing and integrating information that is not natively defined using OO technology. The two most common sources of non-OO information are relational databases and XML.

Rather than add relational or XML-specific features to our programming languages and runtime, with the LINQ project we have taken a more general approach and are adding general purpose query facilities to the .NET Framework that apply to all sources of information, not just relational or XML data. This facility is called .NET Language Integrated Query (LINQ).

We use the term language integrated query to indicate that query is an integrated feature of the developer’s primary programming languages (e.g., C#, Visual Basic). Language integrated query allows query expressions to benefit from the rich metadata, compile-time syntax checking, static typing and IntelliSense that was previously available only to imperative code. Language integrated query also allows a single general purpose declarative query facility to be applied to all in-memory information, not just information from external sources.