Because developing with the .NET framework gives you the freedom to use multiple languages it can be a bit of a hassle to choose between them. VB.NET and C# are probably the most wide spread languages and a question that gets asked regularly on the ASP.NET forums is which one to choose. My answer: learn one of them and when you're familiar with one learn the other. My former company used VB.NET as their default language. In my free time I learned C# though so I became familiar with both. The hardest part isn't actually learning another "dialect" language but learning which classes and namespaces there are available to you is.
Well in aid of those who like to know both languages I found a couple of comparison cheat sheets:
And of course some conversion tools: