I am having trouble tracking down information regarding extending Intellisense. It looks like creating a plugin for VS 2010 or Resharper would do the trick. However, I can't find any documentation for adding items to the intellisense dropdown.
This post got pretty close: How to extend IntelliSense items?
But I couldn't find any documentation for the interfaces or classes being used.
What I am trying to do is to read from an XML file, and add those tags as part of the results that show up in intellisense in the C# code (not in XML).
The part of the R# Plugin Development Guide concerning Code Completion (i.e., IntelliSense) is on our todo list but has not yet been written. When done, it should be available here. While we're working on that, feel free to email me dn at jetbrains dot com, and I'll try to help you out with any queries you might have.