I just released a beta of new Spell Checker plugin version (a plugin for DXCore/CodeRush for Visual Studio.Net). The main new feature is that it does spell checking of XmlComments and Comments, too. Furthermore, different settings and dictionaries can be used for different categories.
So, if you are interested in a free spellchecker for your Visual Studio.NET code, go for it. Feedback is appreciated.
You'll find it here.