Top 20 NuGet web.config Packages

Allows you to work with complex configuration structures in your app.config or web.config files. Doing it the classic way with System.Configuration is difficult and error prone. JJ.Framework.Configuration makes it super easy.
Will help make your code environmentally friendly for testing/quirks (wraps System.Configuration.ConfigurationManager) in a straight forward way.
Reading and writing .net application settings.
xPike Configuration - System.Configuration Provider
Configuration provider for IConfigurationBuilder that adds the config from the old web.config/app.config legacy configurations.