Spell checker for HTML, ASP.NET, JScript, VB, C#, CSS and C++ for Visual Studio 2005 and 2008
Found a MSDN blogger who created a spell checker add in for Visual Studio 2005 and Visual Studio 2008.
Get it here: http://blogs.msdn.com/webdevtools/archive/2007/12/13/spell-checker-for-html-asp-net-jscript-vb-c-css-and-c-for-visual-studio-2005-and-2008.aspx