Where are the Outlook Calendar plugins?

Where are the Outlook Calendar plugins?

I cannot find links to download them anywhere.

I did see one for Outlook 2010.  I tried using it, however it mentioned it was still beta.

And I encountered an issue where although it took the calendar appointments properly, all of the data for the attendees was messed up.  No matter who created the appointment, or who had accepted, it always said I was the originator of the calendar appointment, and no one else was invited.