- PowerCommands - Useful extensions for Visual Studio (Supports VS 2012) adding additional functionality to various areas of the IDE
- DevExpress CodeRush Xpress
- AnkhSVN - Subversion Support for Visual Studio
- Ghost Doc - Simplify your XML Comments
- Visual Studio Color Theme Editor - Make your Visual Studio look pretty with themes
- VsVim
- DPack
- VSFileNav - fast searcher with wildcards + camel case searches
- Sonic file finder - fast and convenient search
- AllMargins
- tangible T4 Editor plus modeling tools for VS2010 adds IntelliSense and Syntax Coloring to T4 Text Templates
- Word Wrap with Auto-Indent
- Indentation Matcher Extension
- Structure Adornment
BlockTaggerBlockTaggerImplSettingsStoreSettingsStoreImpl
- Source Outliner
- Triple Click
- ItalicComments
- Go To Definition
- Spell Checker
- Remove and Sort Using
- Format Document
- Open Folder in Windows Explorer
- Find Results Highlighter
- Regular Expressions Margin
- VSCommands
- HelpViewerKeywordIndex
- StyleCop
- Extension Analyzer
- CodeCompare
- Team Founder Server Power Tools
- VS10x Selection Popup
- Color Picker Completion
- Numbered Bookmarks
- Mouse Zoom
- Visual Studio 2010 Pro Power Tools
- JSEnhancements - provides outlining and matching braces highlighting features for Visual Studio JavaScript editor; provides fantastic #region collapsing in JS and CSS files, making long files much easier to handle;
- Code Contracts Editor Extensions
- WoVS Quick Add Reference
- JScript Editor Extensions
- Align By
- T4 Editor
- Quick Open File for Visual Studio 2010 - quick opening any solution file
- CleanProject - Cleans Visual Studio Solutions
- NuGet - NuGet is a free, open source developer focused package management system for the .NET platform intent on simplifying the process of incorporating third party libraries into a .NET application during development.
Not Free
- Resharper
- Visual Assist X
- JustCode
- ViEmu
- CodeRush with Refactor! Pro
- VisualSVN
- VS10x Code Map - Displays a graphical nested representation of the current editor window code (Supports Visual Studio 2012)
- VS10x Editor View Enhancer (Supports Visual Studio 2012)
Get more details on MSDN: Installing and Managing Visual Studio Tools and Extensions