Wheel Button Instance is a GNOME 3 extension that uses the wheel button to create a new instance of the selected application in the dashboard, on the current workspace. Ctrl-LeftClick creates a new instance on a new workspace. This extension inverts the default GNOME behavior.
The first version of this extension was here: https://gitorious.org/chrisirwin-utils/newinstancecurrentworkspace I asked for a merge request, but I never had an answer so I decided to take charge of the extension.