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.

1. SharpDevelop

   http://www.icsharpcode.net/OpenSource/SD/Download [1]
   An open source IDE for .NET. Check out the full feature tour [2].
   
   
   

2. Visual Web Developer Express Edition

   http://www.microsoft.com/express/vwd [3]
   Stripped down version of Visual Studio that allows you to write .NET web applications.
   
   
   

3. TortoiseSVN

   http://tortoisesvn.net/downloads [4]
   There is no better Subversion client for Windows. You need this if you are going to use VisualSVN with Visual Studio.
   
   
   

4. NAnt

   http://nant.sourceforge.net [5]
   .NET based automation tool that has many built in tasks but could be extended with custom code written in any .NET language.
   
   
   

5. Snippet Compiler

   http://www.sliver.com/dotnet/SnippetCompiler [6]
   Snippet compiler is a small tool to write and execute small chunks of .NET code without creating a Visual Studio project.
   
   
   

6. .NET Reflector

   http://www.aisto.com/roeder/dotnet [7]
   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.
   
   
   

7. Microsoft SQL Server Management Studio Express

   http://www.microsoft.com/downloads/details.aspx?FamilyID=c243a5ae-4bd1-4e3d-94b8-5a0f62bf7796&displaylang=en [8]
   Tool for database administration and development from Microsoft
   
   
   

8. Quest Comparison Suite for SQL Server

   http://www.quest.com/Comparison-Suite-for-SQL-Server [9]
   Compare and synchronize database schema and data
   
   
   

9. XYPlorer

   http://www.xyplorer.com [10]
   Awesome file manager. The older version is completely free.
   
   
   

10. Convert C# to VB.NET

    http://labs.developerfusion.co.uk/convert/csharp-to-vb.aspx [11]
    

11. NAnt Add-In

    http://www.netlogics.ch/devcenter/display/NLC/NAntAddin [12]
    Visual Studio add-in for NAnt integration
    
    
    

12. NUnit Add-In

    http://www.netlogics.ch/devcenter/display/NLC/NUnitAddin [13]
    Visual Studio add-in for NUnit integration
    

More Visual Studio add-ins can be found at 15+ Free Visual Studio Add-Ins [14] and 15+ FREE Visual Studio Add-ins - Part 2 [15]