I recently bought a couple from here, but not had a chance to try as yet. Scroll down the page for links to tech info,
http://www.ebay.com/itm/ESP8266-Serial-WIFI-Wireless-TransceiveR-Module-Send-Receive-LWIP-AP-STA-/251636525924?pt=LH_DefaultDomain_0&hash=item3a96b4ab64