November 2014 - Microsoft have now produced a few Visual Studio Community Ide which works with Visual Micro. For this reason Visual Studio 2010 is no longer supported.
The free Arduino plugin for Visual Studio and Atmel Studio can be downloaded from visualmicro.com
For Vs2012-2015 please see the Arduino for Visual Studio extension in the Microsoft Gallery or via "Tools>Extensions and Updates"
Images might be out of date
http://www.visualmicro.com/

The plugin provides Arduino compatible development and upload using either Microsoft Visual Studio or Atmel Studio.
Download and Documentation
This site is for all open source elements and extensions such as debugger Visualizations for the Visual Micro plugin. We hope you can contribute to the plugins which are functional but very immature due to time constraints.
read more .... Please join the FORUM for help, assistance and optional notifications._
The Arduino IDE for Visual Studio Pro 2008-2013 and 2013 Community (also for Atmel Studio 6.2) provides a free, simple and fully compatible alternative to the Arduino IDE. Installation takes 10 minutes. This solution is suitable for both experts and novices. Arduino for Visual Studio and Atmel Studio Instructions, Documentation and Forum
Project source code remains fully compatible (identical) with the Arduino IDE and the Linux, Mac, Windows open source community.
Atmel Studio is included in the latest release along with support for Visual Studio 2008-2013 and Arduino 0023, 1.0.x and 1.5.x. Currently supports all Arduino versions up to 1.5.6
Visual Micro + Usb Debugger is an optional upgrade that includes faster tools, more flexible build process, better cache control and a unique Arduino usb debugger (read more on visualmicro.com).
An Visual Micro"new releases" forum board provides a list of fixes and functionality changes.
The plugin provides a range of additional visual studio commands such as board and port selection, fully working Arduino intellisense, one-click compile and upload to any Arduino board. Windows 8 users need to enable .net3.5 for the installer to work (or you will encounter error: 10001 when trying to install)
Arduino for Visual Studio and Atmel Studio Instructions, Documentation and Forum
To ensure the full product remains free, if you are using and enjoy this product then please add a comment to this thread in our forum. You don't have to say very much, just say if you like the plugin or maybe explain your experience level and any previous experience of other Arduino development tools. or something else :) Thanks!The plugin installation does not alter your visual studio configuration in any detrimental or permanent manner and works with all Arduino versions (1.5 is beta) . The Arduino plugin is easy to disable or uninstall should you decide not to make use of it. (see the help on the main site for more info).
Please feel free to join us and contribute your open extensions, visualizations and plugins for Visual Micro
Arduino IDE for Visual Studio 2008please note that button and menu icons are a fixed picture in the 2008 version. The example directly below is out of date, see the 2010 example below for a better example

Read more on the visual micro site or visit the forum.
A Visual Micro Limited Community Service
currently supporting Arduino versions up to 1.0.5 and 1.5.4 (1.5.5-r2 in downloads>beta)