NCover: Test Coverage Tool

NCover works with NUnit to compute test coverage on your code. Critical stuff to understanding whether you've got solid coverage of your code. Note that solid coverage using badly written tests isn't a particularly Good Thing, so you'll still need to don your Engineering Cap to write solid tests. See also NCoverBrowser, NCoverGUI, and the enhanced NCover stylesheet.

VBCommenter: XML comments for VB.NET

VB.NET's compiler lacks support for XML comments like you can take advantage of in C#. Check out VBCommenter for a tool which will give you the same critical functionality.

Hanselman's Critical Tools List

Scott Hanselman has a terrific list of tools for the "Ultimate Developer and Power Users"