Cobra- Clean, high-level syntax (Boo/Python-like). Static and dynamic binding. First class support for unit tests and contracts. Compiled performance with scripting conveniences. Lambdas and closures. Extensions and mixins
Eagle- A .NET implementation of theTclprogramming language, built on the CLR.
Essence#- Essence# is a fully dynamic and highly polymorphic programming language which features pervasive message passing, pervasive dynamic and strong typing, pervasive and deep reflection and pervasive object orientation.
F#- A mature, open source, cross-platform, functional-first programming language.
F*- An ML-like language with a type system for program verification.
Language-ext- C# 6.0+ functional language extensions. Make C# more like F# and other functional languages
LINQ Extensions- LINQ extensions for .NET is a collection of useful extensions methods that extends LINQ's capability. There are methods for combinatorics and sequence analysis, generation and manipulation.
AForge.NET- a C# framework designed for developers and researchers in the fields of Computer Vision and Artificial Intelligence - image processing, neural networks, genetic algorithms, machine learning, robotics
OpenTK- OpenTK is a low-level, cross-platform binding to OpenGL, OpenGL ES, OpenCL and OpenAL, available for Windows, Linux, Mac OS X, BSD, Android and iOS.
SharpDX- SharpDX is a project delivering the full DirectX API for .NET on all Windows platforms.
Exceptionless- Provides real-time .NET error reporting for your ASP.NET, Web API, WebForms, WPF, Console, and MVC apps. It organizes the gathered information into simple actionable data that will help your app become exceptionless!
ELMAH- ELMAH (Error Logging Modules and Handlers) is an application-wide error logging facility that is completely pluggable. It can be dynamically added to a running ASP.NET web application, or even all ASP.NET web applications on a machine, without any need for re-compilation or re-deployment.
log4net- A tool to help the programmer output log statements to a variety of output targets.
LogMaster4Net- It is a central log server which can organize your logs in different applications in a same place but have same log behaviors (loggers, appenders, levels and rules) like in the indepedent applications before.
NLog- NLog is a free logging platform for .NET with rich log routing and management capabilities.
Model-View-ViewModel (MVVM) Frameworks
Caliburn Micro- A small, yet powerful framework, designed for building applications across all XAML platforms.
Catel.MVVM- Catel is an application development platform with the focus on MVVM.
MVVM Cross- A cross-platform mobile MVVM development framework.
MVVM Extensions- MVVM cross platform (.NET FW 4.5, WPF, Windows Runtime/Phone) extensions for .NET with support for async commands, MVVM-friendly Object and Task with support for UI notification.
Okra App Framework- An MVVM framework for Windows Store applications including MVVM templates for Visual Studio.
Prism- A cross-platform desktop and mobile MVVM development framework.
Radical- An infrastructure framework whose primary role is to help in the development of composite WPF/Silverlight/WP/WinRT applications based on the Model View ViewModel pattern.
ReactiveUI- An MVVM framework that integrates with the Reactive Extensions for .NET to create elegant, testable User Interfaces that run on any mobile or desktop platform.
Simple Mvvm Toolkit- Provides a simple framework and set of tools for getting up to speed quickly with applications based on the MVVM design pattern.
WPF Application Framework (WAF)- A lightweight Framework that helps you to create well structured WPF Applications. It supports you in applying a Layered Architecture and the Model-View-ViewModel pattern.
API Port- A tool that will analyze code for compatability issues when migrating between .NET Framework releases.
Cake(C# Make) - A build automation system with C#/Roslyn driven build scripts.
ZeroToNine- A tool for maintaining .NET Assembly versions across multiple files.
AutoFixture- An open source framework for .NET designed to minimize the 'Arrange' phase of your unit tests. Its primary goal is to allow developers to focus on what is being tested rather than how to setup the test scenario, by making it easier to create object graphs containing test data.
Fixie- A low-ceremony, convention-based testing framework with flexible customization.
FluentAssertions- A very extensive set of extension methods that allow you to more naturally specify the expected outcome of unit tests and which make your assertions look beautiful, natural and most importantly, extremely readable.
TestStack.Seleno- Seleno helps you write automated UI tests in the right way by implementing Page Objects and Page Components and by reading from and writing to web pages using strongly typed view models.
TestStack.White- White is a framework for automating rich client applications based on Win32, WinForms, WPF, Silverlight and SWT (Java) platforms.
xBehave.net- A BDD/TDD framework based on xUnit.net and inspired by Gherkin.
xUnit- xUnit.net is a community-focused unit testing tool for the .NET Framework.
Autofac- Autofac is an addictive Inversion of Control container for .NET 4.5, Silverlight 5, Windows Store apps, and Windows Phone 8 apps.
Castle Windsor- A mature Inversion of Control container available for .NET and Silverlight
DI Feature Tests- Tests that track commmon DI features among multiple containers
dI.Hook- DI container that allows invocation using AOP
DryIoc- DryIoc is small, fast, capable IoC Container for .NET
fFastInjector- fFastInjector is a high-performing dependency injector, service locator, and/or IOC (inversion of control) container.
QuickInject- QuickInject is a Unity 3.5 based IoC container that aims to give the Unity container a performance advantage in basic scenarios.
Simple Injector- Simple Injector is an easy-to-use Dependency Injection library for .NET 4+ that supports Silverlight 4+, Windows Phone 8, Windows 8 including Universal apps and Mono.
Spring.NET- Spring.NET is an open source application framework that makes building enterprise .NET applications easier.
StructureMap- StructureMap is a Dependency Injection / Inversion of Control tool for .Net that can be used to improve the architectural qualities of an object oriented system by reducing the mechanical costs of good design techniques.
StyleMVVM- Style MVVM is a toolkit designed for the Windows Store platform around the idea of being light weight and fast.
TinyIoC- An easy to use, hassle free, Inversion of Control Container for small projects, libraries and beginners alike.
Unity Container- The Unity Container (Unity) is a lightweight, extensible dependency injection container with optional support for instance and type interception.
Dapper- Dapper is a single file you can drop in to your project that will extend your IDbConnection interface.
Eggado- Eggado takes generics, lambdas, expression trees, dynamic methods and DLR and uses them to breathe new life into data access using good old ADO.NET. It's for folks who can live with a SQL dialect.