Xamarin.Build.Download by: Microsoft

Support for downloading and unpacking archives when building MSBuild projects

YamlDotNet by: Antoine Aubry

YamlDotNet is a .NET library for YAML. YamlDotNet provides low level parsing and emitting of YAML as well as a high level object model similar to XmlDocument. A serialization library is also included that allows to read and write objects from and to YAML streams.

XLParser by: TU Delft Spreadsheet Lab Infotron

A parser for Excel formulas

ZString by: Cysharp

Zero allocation StringBuilder for .NET Core and Unity.