I just found this nice tool called CopyPasteKiller that helps you find duplicate code in your applications. I’ve been a user of Simian - Similarity Analyzer for a long time, but this tool looks promising.
CopyPasteKiller is a free tool for .Net developers that will analyze a directory of code and find large chunks of similar code in multiple locations. This similar code can then be refactored either by creating a base class or by reducing the protection level on the method so it can be called by multiple classes. Technically, CopyPasteKiller should be called CopyPasteFinder because its up to you to remove the duplicate code, but CopyPasteFinder isn't nearly as fun a name as CopyPasteKiller.
I think I have an extra tool in my toolbox from today on.