In case you aren't aware, project files like .CSPROJ and .VBPROJ are really MSBuild project files, and as such, you can edit them to perform additional tasks, include targets, and more. I have often found myself editing them in Notepad because I believed it was the easiest way. As of today I am using Notepad no more, at least for editing project files.
This is because you can work with project files directly in Visual Studio without closing your project, and with full IntelliSense and syntax highlighting. Simply right-click the project node in the Solution Explorer tool window and select Unload Project. Then right-click on the project file again, and select Edit [Project Name]. You can now edit the project file with full Visual Studio editor window support.
When you are done editing the project file, right-click on the project node and choose the Reload Project command.
Simple, eh?