For the script language Python the info after James Henstridge (
http://www.gimp.org/docs/python/) is scattered, here some more.
An article about using Python for GIMP and 'PyDev' plug-in for the 'Eclipse' IDE, written by Nathan A. Good (2011).
http://www.ibm.com/developerworks/library/os-autogimp/Also for debugging 'pygimp' plug-in by 'ofnuts', a member here, see
http://gimpforums.com/thread-debugging-python-fu-scripts .
Edit: sorry for the above, this is not the address any more (2016/11/25)!
For some of your 'pygimp' info, open the GIMP python-fu console and enter 'help(gimp)' and save.