Can you get a wireless booster that you can plug into wall socket?

Yeh I have a laptop at one end of my house and the main computer is at other end. the main computer is connected to the BT Home Hub by the ethernet cable and the laptop just about connects wirelessly to the router. Is there any signal repeaters/ wireless boosters that can act as the "middle man" by being plugged into a wall socket and then the booster connects wirelessly to the main router and then repeats the signal on further?