This article is obsoltete. Please look here for newer version http://blogs.msdn.com/webdevtools/archive/2008/11/29/spell-checker-update-2-2-full-support-for-vs-2008-sp1-simpler-setup-and-a-few-bug-fixes.aspx
List of word to ignore is a Unicode text file and stored in your user roaming profile folder. It is shared across VS 2005 and VS 2008 add-ins if you have both versions installed.
Microsoft Office custom dictionary file is also a Unicode text file that is stored in the roaming profile in the Microsoft\UProof folder
You can either either file in Notepad. Alternatively, you can edit list of words in the Office custom dictionary using Microsoft Word facilities:
Since using custom dictionary and ignore list introduces certain perfomance hit (which depends on the dictionary size), you can turn it off in rules.xml file located in the Spell Checker installation folder (typically C:\Program Files\VS 2008 Spell Checker Add-In ) and change useOfficeCustomDictionary and/or useIgnoreList to 0.
<options> <useOfficeCustomDictionary>1</useOfficeCustomDictionary> <useIgnoreList>1</useIgnoreList> </options>
For multilanguage spell checking, please look here and here. More details on how spell checker works and its various options can be found here.
Important note: Add-in does not work with Visual Web Developer Express as Express editions are not extensible.
Visual Studio 2005 Add-in download
Visual Studio 2008 Add-in download