OK I'm ready to be shot down with this one - I know there have been some cheaper options out there recently, but this has the advantage of a known manufacturer, pass through and an extra adapter.
Usual blurb follows:
For every purchase of this Powerline kit you can claim an extra adapter (DHP-306AV - QF 255614).
D-Link's PowerLine Homeplug AV Passthrough Starter Kit consists of two adapters that use standard electrical wiring to create or extend a network.
You can connect any device such as computers, routers, media players, gaming consoles or storage devices at speeds of up to 200 Mbps over electrical wires, making this medium ideal for streaming high quality HDTV signals and enjoying music and games anywhere in your house. Each adapter has an electrical socket built in, so you don't need to worry about running out of sockets!
Advanced technology built into these adapters makes them more resistant to electrical interference from other household appliances, so users can fully benefit from the maximum transmission speeds.
The adapters also include Quality of Service (QoS) mechanisms to ensure a lag-free experience for delay-sensitive applications such as gaming or Internet TV.
All that is required for set-up is pushing a button on the side of the device. This also ensures secure transmissions between PowerLine adapters. In addition, these adapters are among the first in their category to comply with the European Union directive for office and domestic devices (EuP): when idle, they enter a standby mode that requires less than 1 Watt.