If I post a document in workspace and then share it with some people by putting their email address in there, I can make a comment and send that to the list of people along with their invitation to access the workspace- no problem. But if I add a new document to the workspace, I do not see any place in Workspace where I can notify them that I posted a new document and provide a new comment.  How do I share a notice of an update and a comment about it from within Workspace?   Do I just send a separate email?

I believe the notification feature is only available in Office Live Small Business. Office Live Workspace does not offer this functionality.

People that you share with will automatically get activity updates by e-mail (unless they have disabled this feature through their Activity Feed).

-- David.