the term "plugin" seems to mean a lot of things. If you think about it, a jquery plugin is nothing more than a function or class (both of which are objects) that is attached to either the jquery object or the jquery prototype.
So really, i'm not sure of what kind of tutorial to point you to! a simple class can be made a plugin simply by attaching it to the jquery object.
what kind of plugin are you trying to build? what is the purpose of this class? i may be able to suggest a structure to build on.