Clone Detective for Visual Studio allows you to analyze C# projects for source code that is duplicated somewhere else. I have not tried the tool myself yet, but the idea is really nice. One thing I do not like so far – it needs Java (yes, right, the J-word!) to run.
The tool currently supports only C#, but C++ and VB are promised too, although it is not clear when they will come. Support for these (and some other) languages is already available in the ConQAT toolkit that is used by the Clone Detective, so it might not take very long time.