To find new and working plugins, browse or search xbmc.org forums. This where most of the active python coders are releasing their plugins or scripts. You can also request plugins that are not made yet.

Python Scripts/Plugins Support and Requests

You can also download plugins straight from xbmc by using the SVN Repo Installer

I recommend using xbmc.org forums for up to date news and support for xbmc. I love xbox-scene, but these xbmc sub forums here are practically dead.