[http:The ESP8266 WiFi Module is a self contained SOC with integrated TCP//rancidbacon.com/files/kiwicon8/ESP8266_WiFi_Module_Quick_Start_Guide_v_1.0IP protocol stack that can give any microcontroller access to your WiFi network.4The ESP8266 is capable of either hosting an application or offloading all Wi-Fi networking functions from another application processor.pdf Quick getting started guide]
[http://hammerproject.com/post/130804023369/iot-intro-sms-me-when-i-leave-my-garage-door-open Example project from a-z for beginners], [http://rancidbacon.com/files/kiwicon8/ESP8266_WiFi_Module_Quick_Start_Guide_v_1.0.4.pdf getting started guide] [https://github.com/nodemcu/nodemcu-firmware NodeMcu] is a great higher level interface and easier to use than the default one. You can also do this through [https://github.com/micropython/micropython/tree/master/esp8266 Python] and [http://www.esp8266.com/wiki/doku.php?id=loading_firmware other means]. [http://www.ebay.com/itm/ESP8266-Serial-WIFI-Wireless-Transceiver-Module-Send-Receive-LWIP-Support-AP-STA-/171653455849 Currently cheapest eBay listing (2.40 CHF)]. Available under $2 in bulk.
http://hackaday.com/2015/03/18/how-to-directly-program-an-inexpensive-esp8266-wifi-module/
=== Flashing ===
How to talk to your RPi (and wiring) [http://www.extragsm.com/blog/2014/12/03/connect-esp8266-to-raspberry-pi/]
There are quite a few examples of how to use the ESP on the [https://github.com/nodemcu/nodemcu-firmware#start-play nodemcu] page, to be able to control LEDs or relays over wifi, you'll need to [https://github.com/nodemcu/nodemcu-firmware#connect-to-your-ap connect it to wifi], set up a [https://github.com/nodemcu/nodemcu-firmware#with-below-code-you-can-telnet-to-your-esp8266-now telnet server] (hint: load it as a init.lua script), and then [https://github.com/nodemcu/nodemcu-firmware#manipulate-hardware-like-a-arduino manipulate the GPIOs].
=== Resources ===
* [https://hackaday.io/project/5673-esp8266-dash-button ESP8266 Amazon Dash button]
* [http://hackaday.com/2015/03/18/how-to-directly-program-an-inexpensive-esp8266-wifi-module/ How to directly program an inexpensive ESP8266 wifi module]
* [https://www.youtube.com/watch?v=7BYdZ_24yg0 ESP8266 outdoor range test (hint: very far)]