NuGet Package Explorer (NPE) is an application that makes it easy to create and explore NuGet packages. You can load a .nupkg or .snupkg file from disk or directly from a feed such as nuget.org. Even with the added functionality in Visual Studio to generate NuGet packaged in a build the tool is extremely useful if you are working with NuGet packages.
You can find out more about the application at its GitHub repository (https://github.com/NuGetPackageExplorer/NuGetPackageExplorer). Scroll down to the README.md documentation for information on installing the application.