When is the best time to take dormant cuttings. Right after the tree loses all its leaves, a few weeks after, or months after? 

Cuttings could be taken any of those times with success.  However, it seems to be more common to wait until late winter.  Presumably this is to allow the tree to get the necessary number of chill hours.  Another reason is that if you take cuttings now you will need to figure out a way for the rooted/leaf-out cuttings to get the necessary amount of light as you grow them in-doors.  If you take them in February by the time they reach that stage you may be able to start putting them outside during the day.

Steve

I see you are in MD also. Do you cover your trees or store then away? I put two of my smaller ones in a unheated uninsulated shed and left the larger ones outside unprotected. I live near Rockcreek park and we have been getting regular heavy frost, that stick around until 10AM easily in the shade.  Think this is ok? 

I assume your bigger ones are in pots and a little bit older.  The roots shouldn't freeze.  Worse than the regular frosts is the frost/warm cycles.  Even worse is if it warms up for a while and the tree puts out tender new growth that's then killed by the next frost.  For that reason it's better off in the shed where it will be less tempted to leaf out.

Frank, yes I'm just a few miles from you.  Last winter was the first winter I had to deal with this since I started rooting my first cuttings December 2010.  I protected my one in-ground tree with a couple layers of carpet and a white tarp.  The container trees went into an unheated garage.  My garage is not insulated though I'm not sure how much difference that would make.  There was no damage to any of my trees but then again it was a very mild winter.  It sounds like all of your trees are in containers.  If it were me I would definitely move them all into the shed.  One of the main advantages of growing in containers is the ease of winter protection, right?  You certainly could enhance their protection by wrapping but the safest and easiest way to go, it seems to me, is to bring them into an unheated structure.

You ask when best time to take cuttings ?
In my experience for "storing" when tree goes dormant and sap no longer runs.

Best time to take cuttings for propagating right away i have had the best hits right before tree makes budbreak.