Info on the guts of the esp8266 EcoPlug/WorkSmart CT-063w WiFi Smart Socket with energy monitoring made by KAB, available from Wallmart. Also sold as WiOn from Pegasus Lighting. Module appears to be used in wall switches, as well.
Info on hacking a kankun Atheros-based wifi socket running OpenWRT
Source: kankun – How to Linux
More info on local control of Orvibo S20 Socket
Good info on hacking/spoofing the Orvibo S20 WiFi socket. Unfortunately, it appears that the security of the cloud service is (was?) really bad.
Report on using Sonoff with alternative Sonoff-Tasmota Firmware
Source: Review of Sonoff RF Bridge, Sonoff 4ch Pro, and Sonoff POW with Sonoff-Tasmota Firmware
Code to allow OTA installation of alternative firmware on Sonoff devices, avoiding the need to connect to the serial port.