Ursus (nuget): A library that makes it easier to persist and apply stored application state (window locations and sizes, user settings and preferences, etc).   Instead of writing code that moves data back and forth from a .settings file, just specify which properties of which objects need to be persistent (in one of several ways), and you're already done.   There's no magic, you can control almost everything about the process, all it does is save you from having to write a lot of tedious code.   Even though the library is tiny (<1000 LOC) it means serious business, it's powerful, highly customizable and provides many extension points, but comes with all the basic functionality built in.   The source repository is on github, and there is an article describing it on codeproject (check the project url). The article is a bit dated compared to the library code though.
Keywords: .net|settings|state|persistence|wpf|winforms|asp.net|mvc