If the workspace  was created  through an Outlook invite, or if you have
synced the appointment with Outlook, then you can open the entire  series
in Outlook and add  additional users  to the Invitation. If you open the
first instance of the meeting  it will add those new invites to the
attendee list for every meeting in the workspace. I have never found a
way to do this from inside the workspace itself.

I am sure that we tried this... I am starting to have a feeling that
this is another 'gotcha' from still running in an Outlook 2003 / MOSS
2007 environment but was hoping that there was a workaround.

I forgot to ask. Yes, this would require Outlook 2007, not
2003.

So, did I really stump everyone on my very first question to this
forum or is there no way of adding  attendees to all of the recurring
meeting workspaces once the meeting/workspace has been created.

The natural place for changing this setting would be in Advanced
settings for the list, under the heading "Share List Items Across All
Meetings (Series Items)".

But when I opened up a MOSS environment for verifying this it turned
out that the "Yes" button is not enabled for the Attendees list.

So, to me it seems that the chances for having this functionality OOB
are rather slim.