This is my list of indispensable tools for the development with .NET:
- Aqua Data Studio
- CoolCommands for Visual Studio 2005
- CruiseControl.NET
- DPack
- FxCop
- NAnt
- NCover
- NDoc
- NMock
- NUnit
- NUnitAsp
- Reflector
- Reflector FileDisassembler Add-In
- TestDriven.NET
- Visual Studio 2005 Code Snippets
- Visual Studio 2005 Test Code Snippets
- Visual Studio 2003 Bootstrapper
- Whidbey Commands for Visual Studio 2003
- XML Visualizer for Visual Studio 2003
UPDATE: More tools here.