Scott Hanselman has compiled a great list of .net tools a Developer must have...
It includes few of the ASP.NET Must Haves and Visual Studio add in's like -
UrlRewriting.NET - An open source URL rewriter, implemented as an HttpModule.
Web Development Helper - that allows ASP.NET 2.0 built into a Browser Toolbar.
Blinq - A tool for generating ASP.NET websites for displaying, creating, and manipulating data based on database schema.....and many more Visual studio add in's.
Check for details at his site at: http://www.hanselman.com/tools