My friend Andrea (bimbomix1) has suggested to me to use XPairtise.
What is XPairtise? It's a fantastic eclipse plugin for remote pair programming in a complete XP-style! The plugin concurs to share and modify the same code like a driver (who write the code) or navigator (who suggest the code). A comfortable perspective provide a chat session, a blackboard for notes and sketches, and a little project manager. Like in a true pair programming session, the navigator can't write code (the keyboard is locked by XPairtise) until the driver switch the role with the navigator (for example at the end of Pomodoro...).
Use the plugin with Skype (for talk between pairs) is very cool and useful, but Isn't a real substitution for the real pair programming.
You can get it here