The September CTP of "Orcas" in the form of a Virtual PC image is now available on MSDN Subscriber downloads. It's not for buillding production systems, but for evaluation.

Here's a list of highlights:

• Improvements on the widely acclaimed Visual Studio 2005 product set
• Significant investments in improving product quality
• LINQ to Objects API
• LINQ to Objects API supports queries over any .NET collection, such as arrays and Generic Lists. This API is defined in the System.Query namespaces inside System.Core.dll. Click here for more details about LINQ.
• Partial C# 3.0 Language Support: This CTP implements some of the new language features of C# 3.0
• Local variable type interface
• Lambda expressions
• Object initializers
• Partial C# 3.0 IDE Support: In addition to the C# 3.0 language features there is partial IDE support
• Colorization and New Keywords in Completion List
• Edit and Continue Rude Edit Detection
• VSTS Improvements in load & unit testing such as unit test for devices
• Device development improvements
• VSTS integration
• Access and modify device security configuration from the IDE
• Enables developers to build and debug a Windows Vista Application
• Enables Visual Studio Tools for Office developers to build document-level customizations for Word and Excel 2007
• Enables eMbedded Visual C++ 4.0 developers to use Visual Studio Code Name “Orcas” to build their existing applications NET Framework improvements such as:
• New managed add-in model enables developers to add a version-resilient extensibility model to their products.
• Support for time zone conversion, enumeration and serialization, including cases where Daylight Saving Time rules change over time.
• Reflection in Partial Trust, enabling sand box scenarios for all applications that depend on these features.
• The ability to control the garbage collector’s latency mode
• Improved CLR ThreadPool micro-performance and throughput for worker and IO completion

Link to MSDN Subscriber Downloads