You can download the latest version of IdleX here or at the SourceForge page:
To run IDLE with IdleX, unzip and then run idlex.py. It will work with Python 2.6+ or 3.x series.
Take a look at the demos directory to see how IdleX extends IDLE. More information can be found under Extensions.
IdleX is also available on PyPI. It may be installed with pip or easy_install.