Originally, Gimp only supports script-fu plugins which are written in lisp. From some day that I don't know exactly, Gimp started to support plugins written in python. As a python programmer, I can easily write something for my own purpose. By reading the instructions of the following links, a simple plugin can be written within minutes. However, I do not find many useful examples on the internet. If there's a place on internet to store all the plugins, that would be wonderful.
HOW TO WRITE YOUR OWN PYTHON-FU PLUGIN
1. copy one script from the second link
2. modify the contents as you want, by following the API documentation
3. try out in Gimp
4. add more stuff by referencing PDB browser
Basi Python-fu API Documentation