The HomePlug networking standard isn't all that well known, but it does provide a very quick and easy way of setting up a network at home or in a small office.

A Netgear Homeplug AdaptorHomePlug devices can send network data along your existing electrical mains wiring in much the same way that ADSL connections send the data along an existing telephone line.
The HomePlugs supports data rates up to 85 Mbps and are particularly well suited to homes with thick walls or steel obstacles where wireless transmission can be poor. The very portable nature of the HomePlug means it's easy to have network access anywhere around the house. It's a scalable solution, you can add another HomePlug to network enable another computer.
HomePlugs give a very good connection because, unlike wireless, the quality of the HomePlug is not impacted by radio waves, thick or metal walls or other electrical devices (note that the range of the HomePlug depends on the interferences on your power cabling and the quality of the electrical installation, generally they are suitable for any sized house).
Of course, to ensure your networking requirements are met, you can use any combination of wired, wireless and HomePlug LAN products or devices that conform to the IEEE 802.3 networking standard.