When I first heard about powerline adapters my jaw hit the floor, I had no idea that you could transform the wiring in your house into a communication network. You simply plug a powerline adapters into an electrical socket and plug another adapter into another socket and voila the two adapters can talk to each other.
This system is great for houses or buildings that have thick walls that Wi-Fi can't penetrate or want a connection that's stronger than one that originates two rooms away.
The ZyXEL PLA5205 is a great place to start if you are looking to set up this style of network. With that said other powerline adapters have more Ethernet ports on the adapters and a few even automatically create additional Wi-Fi hotspots.
You can get the deal from Ebuyer.