Over my course of .NET development, I have compiled a list of essential free tools for .NET applications. This is not a the alpha or the omega of tools, just a short list that I feel is essential.
An open source IDE for .NET. Check out the full feature tour.
Visual Web Developer Express Editionhttp://www.microsoft.com/express/vwd
Stripped down version of Visual Studio that allows you to write .NET web applications.
There is no better Subversion client for Windows. You need this if you are going to use VisualSVN with Visual Studio.
.NET based automation tool that has many built in tasks but could be extended with custom code written in any .NET language.
Snippet compiler is a small tool to write and execute small chunks of .NET code without creating a Visual Studio project.
Reflector is the class browser, explorer, analyzer and documentation viewer for .NET. Reflector allows to easily view, navigate, search, decompile and analyze .NET assemblies in C#, Visual Basic and IL.
Microsoft SQL Server Management Studio Expresshttp://www.microsoft.com/downloads/details.aspx?FamilyID=c243a5ae-4bd1-4e3d-94b8-5a0f62bf7796&displaylang=en
Tool for database administration and development from Microsoft
Quest Comparison Suite for SQL Serverhttp://www.quest.com/Comparison-Suite-for-SQL-Server
Compare and synchronize database schema and data
Awesome file manager. The older version is completely free.
Convert C# to VB.NEThttp://labs.developerfusion.co.uk/convert/csharp-to-vb.aspx
Visual Studio add-in for NAnt integration
Visual Studio add-in for NUnit integration