Layaway was already available at some stores last Christmas and is actually a very dated offering, but with the bad economy it has found new popularity. Layaway allows buyers to put a product on hold and pay it off over a set period of time. With the final payment they can take the purchased product home.
Layaway is offered by several stores including ToysRUs, Sears and Kmart in stores and on select products.
The Sears Holding, which also runs Kmart is now expanding Layaway to products sold in their online shops.

Layaway helps when you are cash strapped or have an over extended credit card. You still pay more at the end as retailers charge an initiation fee for a layaway plan.
All layaway plans differ in detail and you need to look carefully at what the requirements are and what for instance the cancellation fee costs. More details on the online Sears and Kmart layaway plans can be found here.

There is also a 3rd party online layaway service that offers Layaway on products bought at stores that do not offer layaway themselves. eLayaway charges a 1.9% flat transaction fee on the layaway plan and works with shops including Amazon, Apple store, and Best Buy.