Resharp is an add-in for Visual Studio .NET 2003 that brings intelligent C# code editing, highlighting and refactoring features to Visual Studio. ReSharper aims to provide C# developers with the same level of power and productivity enhancements that have been available to Java developers using IntelliJ IDEA.
ReSharper is currently under development but most of features planned for the release are already implemented. Planned date of ReSharper release is June 20, 2004.
The features are quite long so visit their site to know more. You can also participate to an early program, so you can download a preview for testing.
http://www.jetbrains.com/resharper/