I've seen similar questions but I'm not limiting myself to any particular type, I just want to have a wide swath I can look at. They can be oriented towards ASP.net or not. I know Visual Basic.net already, but haven't started to write any actual real pieces of software yet (I have written my own web sites from scratch though).
Please also say WHY you believe it is some good source to follow.
You could see if the Paint.Net source code is still available. It's more C# than VB AFAIK, would be definitely a great place to look for an experienced .NET coder.
I'd say that
is a fairly sizable and mature project specifically written in VB.NET.
It's a good one to look at as it's quite a large project, has been around for quite some time, and has a reasonably good architecture to it as well as having a good module/plugin system (to allow other developers to produce plugins for DotNetNuke in any .NET language).
In fact, it's probably the only "enterprise CMS" system written in .NET that's been done in VB.NET rather than C#.
Check out the website, and specifically the sections under "DotNetNuke Architecture" for other benefits.