Visual Studio 2010 offers a collection of extensions that help the developer's life.
In this list I try to share some that I hope will help you as they have helped me.
Visual Studio Achievement Extension
This extension is less useful than the whole list, but one of my favorites.
NuGet Package Manager
This is a package management system for the platform. NET that simplifies the inclusion of third-party libraries in your projects. The included libraries are automatically updated.
Productivity Power Tools
The first extension that I installed on my dev machine. 
PowerCommands for Visual Studio 2010
This extension adds many features to the IDE.
VSCommands 2010
Navigation and generation code improvements.
Code Compare
With this extension you can compare code (in file and folder) very easily.
GhostDOC
I use this extension since many years and I can’t live without it.
It creates XML documentation from comments.
If you found other interesting extensions, do not hesitate to contact me!