To provide an update and a more thorough answer; Blizzard recently announced the addition of Kanai's Cube, which has been available on the Player Test Realm this month. It is set for release to the main game in August 2015.
If you are familiar with the Horadric Cube in Diablo 2, Kanai's Cube will feel similar but performs radically different functions.
In Diablo 2, the Horadric cube was used primarily to:
- Combine Gems
- Combine Runes
- Combine potions
- Open the secret cow level
- Modify/reroll weapons and armor
Many of those applications have been supplanted by the gem combiner and enchantress in Diablo 3. Kanai's Cube instead will probably have recipes for (based on the PTR realm's experience):
- Extracting legendary powers
- Completely re-rolling items
- Converting set items to different items from the same set
- Opening secret portals to other levels (such as the Vault)