You have to have a low-cut top to see it.

ya like mine *puffs out chest

If I recall correctly, it doesn't show up in the Clothing part of Wardrobe, but it's still there so after you saved your HA and view it in forums/etc. you can see the cleavage.

and some wearables, e.g. Archduchess Chemise, come with a pre-drawn cleavage line, so a cleavage shows up when you put it on in the Wardrobe .

Well sometimes it is a layering problem, I see this on some HA's on site. Say if you are wearing something covering your whole arm (let's say arm warmers) and the chest area is covered and the arm warmers are covering the chest appears flat.

anyone know of any other specific items that allow for cleveage?

The archduchess under clothing gives massive cleavage (I am wearing the under dress at the moment!)

Bottle of Body Oil really makes the HAs cleavage show a lot more.

The Party Dresses ( / etc) gives cleavage as well. (because it's your thread) (because you asked.