4x D-Link Powerline AV 500 (4x D-Link Powerline AV 500) - $100 for all four (will include the supplied ethernet cables, and a driver CD.

http://www.dlink.com/me/sr/support/product/dhp-500av-powerline-av-500-adapter 

Brought of Chiefe a couple of months back.

Work well, but my house has 2 separate power circuits, and they don't work well across circuits.

On the same power circuit I've got 100Mb out of them. Can stream legally acquired blurays over the network.

All 4 work together on the same network.

Getting some wiring installed, and upgrading to UniFi AP's instead - just what I was trying to avoid.