Recently, the developers landed (by default) Ubuntu (Unity) Web Apps' infrastructure in Quantal Quetzal, without use cases, meaning, there weren't actual Web Apps available (by default), excepting Ubuntu One Music and Amazon, two interesting Web Apps situated on the Unity launcher (without further actions, such as dragging & dropping their launchers on the Unity launcher).
The latest updates bring numerous specific Web Apps in Ubuntu 12.10, allowing users to benefit Web Apps.