We’ve long since had plans to develop our own home automation setup, but with Hristo Borisov’s well documented work, that may not be necessary. His project, titled Switcher, is an open source Wi-Fi power switch, with multiple uses.
Based around an ESP8266-01 (remote serial port Wi-Fi transceiver), Hristo provides a full set of schematics, code and PCB designs. Everything you need to do put this system together yourself. He even provides 3D printable casings. While based on the EU standard plugs, this should be easily modifiable to operate with an American plug. Although you’ll additionally have to fiddle with the triac and linear modulator circuitry to make it happy with the US 110V.
Network commands are sent using HTTP GET, and source code for an iPhone app are available.
More details provided on Hristo’s website.