ESRI Online Trainings
Tutorial for creating Add-Ins in ArcGIS 10 (link)
ArcObjects Help for .NET developers (on-line version of what installs with SDK) (link)
ArcGIS Desktop Help 9.3 (VB .NET example code) (link)
ArcGIS Desktop 9.3 .NET Resource Center (VB .NET examples) (link)
Customizing ArcGIS Desktop using VBA 9.3 (link)
Reference for ESRI built-in command, menu, or toolbar. Use this if you want to add an ESRI element to your custom toolbar (link)
Configuring development environment to develop ArcGIS 10 add-ins - see Environment_Setup ppt attachment on this page
Connecting to ArcGIS license server from off-campus (link)
Sharing Visual Basic solutions (link)
Converting VBA code to VB .NET (link)
NUnit test framework (link)
MSDN documentation on form controls (link)
W3C Introduction to XML (Add-in configuration files are written in XML) (link)
.net Naming Conventions and best practices (link)
ArcGIS user forums (link)