1. FluenthttpclientA modern async HTTP client for REST APIs. Its fluent interface lets you send an HTTP request and parse the response in one go.
2. SmapiThe modding API for Stardew Valley.
3. PredicatesecurityProvides relational security on content collections (including deferred LINQ queries for NHibernate or Entity Framework). This lets you define security groups and permissions using LINQ criteria, and then filter collections based on these security rules.
7. NaturalTimeParserA partial C# implementation of natural time formats like "last month +3 days" which can be used in date arithmetic.