Richard over at ESP8266 CommunityForum writes,
I have setup a new section for ESP8266 Arduino as IGRR and myself have successfully ported the Arduino IDE over to the ESP8266 and have it all working very nicely now. ESP8266 Arduino and the code is on github, we have also set up a compilation server and executables will also be available for download. So go to town and start writing Arduino code the ESP8266! Get your ideas off the ground in no time! FAST!
Arduino IDE released for ESP8266 – [Link]