These are the Visual Studio plugins I use on a daily basis.

Code Refactoring Plugins:

ReSharper: (cost) the best code refactoring plugin for Visual Studio I have ever seen.

AutoCode: (free) never used it but its a free alternative to the expensive ReSharper.

CodeRush Express: (free) similar in function to ReSharper, for free its a pretty good tool.

Other Plugins:

GhostDoc: Free Visual Studio plug-in which adds a keyboard shortcut for adding auto generated documentation comments to your classes and methods.

CodeKeep: (free) online source code snippet repository which has a Visual Studio plugin for easy saving.

CodePlex Snippets: (free) not a plugin but a ton of Visual Studio code snippets which show up in your intellisense for quick code generation of structures you often use.

CopySourceAsHTML 3.0: (free) allows one to copy source code from Visual Studio and paste it into their blogs as html retaining the source code styles.

SmartPaster: allows you to select how you want to insert items off the clipboard (comment, region, etc.)

SnippetDesigner: assists you in creating your own Visual Studio code snippets for auto code creation.