I submitted feedback to Apple for OS X titled: Original Implementation of Stacks regarding Design/Ease of Use. If this is something you would like to see, please do the same. In the original keynote demo of Stacks, included was the ability to grab a group of applications from the finder and place them in a single "application stack" in the Dock - on the left side of the 'crosswalk'. This would allow for the categorization/grouping of applications in the Dock, such as Office Productivity, Audio, Video, Utilites, etc. However, this feature was taken out before the final release of 10.5 Leopard and would be much welcomed back in a later update to the system during the 10.5 update cycle.