One of the things I love about Visual Studio 2008 is the ability to refactor and reorganize the "using" directives in source code files (this may have been in 2005 as well, I don't remember).
Specifically, I'm talking about how you can have it both reorganize the directives to be alphabetical (though with the core FCL libraries floating to the top) and removing any directives which don't need to be there (either never used or no longer used).
Is there any way to automate this refactoring (the sorting and trimming) across an entire old codebase? Either through all of the files in a solution or across multiple solution files.
I believe you can do it solution wide using Power Commands
From PowerCommands Documentation:
Remove and Sort Usings This command removes and sort using statements for all classes given a project. It is useful, for example, in removing or organizing the using statements generated by a wizard. This command can be executed from a solution node or a single project node.