I recently published a new screencast for Office developers.  This brief (6 minutes) screencast walks through creating two different Excel add-in projects that add controls to the same group on the same tab within Excel. 

Since I had been asked a few times, and seen the question coming up more often on discussion lists, I thought it was worthy of a quick screencast.  I will be publishing two more screencast's in the next few days.  One on the new VSTO Power Toys and one on Placing your controls/group in a specific location on an existing tab in the ribbon bar.

Here's my current VSTO related screencast's: