Is there a way to make a linked duplicate object at as a mirrored object? Modeling a woman for example. If I create the first breast then create a linked duplicate, I want to tweek the boobie as it were and if I move a vertex one direction I’d like the same vertex on the linked duplicate to move in the opposite direction. So a grab and move to the right on the right breast would move the same vertex with a grab to the left to retain consistency. Thanks!
in front view, select the object, alt D, RMB, S, X, then move it where you like.
ding twice the viewing pleasure.
yes. Alt D willl give you a linked object so changes in one effect the other.
But for example if you have a plane and alt D it then move it aside, when you move the right upper corner vertice to the right the linked object will do exactly the same. Which doesn’t seem to be what you want. So try this,
say you have a plane out of edit mode. Alt D to duplicate. Then put it where you want , press s then x to mirror it. Then in edit mode when you move the right object upper right vertice to the right the left objects upper left vertice will move to the left.
paradox
I type too slow it was already answered in a more simple manner as I typed. 
one might say
:D:D:D:D:D:D:D
Thanks a bunch guys. Can you clarify some of the commands for me please:
alt-D : Create linked duplicate object
RMB : Why?
S : Scale?
X : delete?
Sorry 4 being a n00ber, but I dont understand the process you guys have explained.
Alt+D : create lined duplicate object (shift-D non linked duplicate)
A linked duplicate only will be made if you have checked the Mesh button in the Edith Methods subwindow of the Preferences window (i-Icon; top window, maybe you have to pull it down).
RMB: is for selecting objects and quitting operations. With Alt+D you make a duplicate and enter the grab mode where you can move the copy around. Because you dont want to move the copy you quit grab mode with RMB.
S: Entering the scaling mode, followed by X-key means the object is scaled -ITS SIZE (i.e. 1 to -1) along its local X-axis, which is the same as mirroring at the YZ-plane. (Blenders mirror function is a scaling).
S follwed by Y-key would do the same with the y-axis, meaning a mirroring at the XZ-plane.
Before making a duplicate and a mirror object I recommed to apply size/rot (Alt+A). This makes the local axis parallel to the global one and avoids confusion for mirroring.
X: x-key alone is deleting. X after S is mirroring.
Tordat,
Thanks for the clarification. I am going through the GUS tutorial in the online manual. I guess I should have started there. Thanks much for the love guys!
g_M_e