Just recently, I ordered two of these: Actiontec MegaPlug 85 Mbps Ethernet Adapter. Basically, they’re ethernet adapters that use your household circuitry instead of wires or a wireless network.
Within three minutes of opening the box, my computers were transferring files nine times faster than the best rate I could get over my wireless router, without having to run wires between the various rooms in my house.
I was dubious, but I’m a convert now.