Well for .NET you could also try VS2010 Beta 1 and the Architecture Explorer (Arch Explorer screen shots).
As for VB6, I'd like to have a tool for that also. This tool from Microsoft Visual Basic 6.0 to Visual Basic .NET Upgrade Assessment Tool
creates a call graph in HTML for a single VBP, not sure how useful it would for you. Other than that I have not found may tools for VB6.
