Are there any good Unity Editor Tools Tutorials out there? How to extend the editor?
I don't really get what you want to know. Do you want tutorials how to use the Unity editor or how to write editor scripts?
If you plan to extend the editor i guess you won't find any tutorials on that. All you need is the scripting reference, google and some programming knowledge. I would recommend using C# since some of the editor classes are not or not well documented. Visual Studio have intelliSense that show you all existing classes including all public variables and functions.
The recourses on unity3d should point you in the right direction:
For further information have a look at these tutorials. The first link shows you many different Editor scripts ready to use where you can use a lot of code for different things: