More than a year ago, I tried out the ESP8266, but didn't get very far. The scene and products have evolved a lot since then, and today it's as easy to use and develop with the ESP8266 as with the Arduino. Some shields are also coming online, although there are no common form factors yet.
DealExtreme stocks a number of different boards and chips. Among them, the most interesting are the various boards from Wemos. They have a two form factors: The "D1", a rather large board which matches the Arduino Uno layout and header pins; and the neat and small "D1 min" at only 34x25 mm. What makes the latter very appealing, is a range of small shields which stack on top of each other, just like the old Arduino.
There are already several interesting shields available from Wemos. Including a temperature sensor; 64x48 pixel OLED display; 220 V relay; motor driver; SD card; battery connector; single button; single LED; and a DIY "proto board". These are not available from DX, and are best ordered from Wemo's AliExpress shop. Please note, the ones linked here do not have the header pins soldered, so a bit of manual soldering work is required.