Here are listed some of the existing companion tools for .NET development.
Although quite comprehensive, this list is not exhaustive. You can submit new tools or report a dead link by dropping me a line.
Note: I have to restrict myself to tool products, and avoid components, class libraries, articles, techniques... otherwise the list would be way too long! That does not mean that I won't make exceptions if I decide to cover a particular area (probably I did already ;-) ).
Chad Osgood has created an RSS feed for this list. Check it out right now to keep informed when the list is updated.
Code generation
Compilation
Obfuscation
Decompilation
Object browsing - Assembly viewers
Refactoring
Persistence and data-related code generation
See also "RAD Tools - Application Development Automation" below
RAD tools - Application development automation
Modeling - Software design - Architecture - Model driven architecture - UML
IDEs - Code editors - IDE add-ins for code edition
Builds
Testing
Code analysis - Standards verifiers
Profiling - Monitoring - Performance Testing - Optimization
Documentation - Code commenting
Frameworks
MVC
AOP
Code versioning - Source control
Localization
Reporting
Page templating
Scripting
Installation
Regular Expressions
Mainframes - Legacy Systems
Code conversion - Language migration
Others
Useful links