The Ozdust Ballroom was a ballroom near the school of Shiz University.
In the musical Edit
In the musical, the Ozdust is first mentioned in "Dancing Through Life." While Fiyero is impressing everyone with his philosophy of being dumb, he asks, "So, where's the most swankified place in town?". Galinda replies with "That would be the Ozdust Ballroom." Fiyero then throws a party at the Ozdust for all of Shiz. This is where Boq tries to confess his true feelings to Nessa but fails, and then Elphaba is also humiliated, but Galinda is there to stick up for her.
The Merchandise Shop Edit
At the musical, the merchandise shop is also named the Ozdust, but it is a boutique. You can buy everything from shirts to necklaces to beach towels.