http://www.esp8266.com/viewtopic.php?f=13&t=605&start=10#p6441
In addition to breaking out all esp-12 pins on .1" headers, it also includes a power status LED + six red ones + an RGB one on GPIOs, and a photoresistor on the ADC.
Close jumper to flash it, open it for normal use. Simple as that. About $6.00.
My second choice would be a NodeMCU Devkit.