Add Wi-fi and web capabilities to your project with this module which is currently in rapid development.
The onboard firmware can and should be updated to the latest available. http://www.electrodragon.com/w/ESP8266#Tools_and_how_to_update_firmware
is a good source of information and provides links to firmware and tools.
Kevin Darrah also provides an excellent video tutorial at http://youtu.be/qU76yWHeQuw
Also see the community forum - http://www.esp8266.com
The module operates at 3.3V, so level shifting may be required.
We have used the PL2303HX USB to TTL serial adaptor (M029), which operates at 3.3V, to carry out firmware upgrade and AT command communications tests with our first samples.
Note: The module needs a 3.3V supply capable of supplying bursts of current up to around 350mA. Do not use the output from an Arduino - it just isn't up to the job.