How to open a specific pane in system preferences from dock?
In Finder, open /System/Library/PreferencePanes on Lion for the system preference panes or /Library/PreferencePanes or ~/Library/PreferencePanes/ for user-added ones.
Drag the icon of your choice from the folder to the Dock. It will probably only go on the right side (the documents/folders/minimized windows/Trash side) of the divider.


Clicking the new icon will open System Preferences directly to that preference pane.