Open Source .NET libraries that make your life easier
To add to the author's list:* I seem to install Json.net in every .NET project I create (json serializer - thanks James Newton-King!)* NLog for logging. It's fantastic.* Dapper is also excellent (Micro ORM) (and anything written by Marc Gravell is generally top-notch - see protobuf-net, miniprofiler, StackExchange.Redis)* Automapper, to avoid writing boilerplate code to convert between similarly shaped types (E.G. DTOs to DB models).* RestSharp makes talking to RESTful apis easier.* Microsoft's Unity is a great IOC framework, although most people seem to use NInject.