Question: I have a requirement to document the assembly dependencies in a vb6/dotnet application.

What techniques / tools are good for performing this sort of document.

I was planning on using Visio for drawing.

Answer: 
Have you had a look at [NDepend](http://www.ndepend.com/)?
Dependency visualizer is good for small projects. For projects or solutions with many inter dependencies it becomes too clumsy to even trace the dependency graph.