I needed to spell check a number of files in a project I'm working on. I wanted to spell check the comments and source code but the spell checker add-in that I had been using only allowed me to spell check selected text and it would complain if the selected text contain any code or comment blocks. So I googled for something that could spell check everything comments and code.  I found a winner, Spell Checker for VS.NET 2003 Add-in (v. 2.0), which is the best spell checker add-in I've ever used (I've tried a handful) and best of all it's FREE.

"This freeware Visual Studio 2003 add-in provides a multi-language spell checker for your comments and string literals. Without setting any options it knows how to spell check C#, VB.NET, C/C++, C++.NET, J#, HTML, XML, Java, and other text-based files. It works on the selected code or on the entire current file or project, and has many other options."

And to top it off, unlike most freeware products who ask for donation to the author, Dean J. Giovanelli asks you to donate to his favorite charities.