(Rhino 4 .NET plug-in development pages can be found here)
The Rhino 3 .NET SDK never made it past a "Work In Progress" (WIP) stage project. This can be downloaded from the Rhino Plug-Ins WIP web page
VBCircleUI - How to display a modal dialog in a command using VB.NET
TestMove - How to move objects using VB.NET