I just received two off these small ESP-01 boards.
They are part off the ESP8266 family and have relly nice specs:

• ESP8266 chip.
• 2 dedicated GPIOs.
• Serial comms (or 2 additional GPIOs).
• Pin connectors.
• Arduino-compatible.
• PWM, I2C, UART, OneWire.
• On-board WiFi + printed antenna, 802.11 b/g/n, 360m range.
• Able to become a wireless access point.
• Lua and Arduino firmware available.
• Able to run a web server.
• Dimensions: 24.75 x 14.5mm.
• Power: 3.3v. (important!!)

Sources: http://esp8266.co.uk/modules/esp-01/

Instruction for flashing this little fellow can be found on http://www.esp8266basic.com/flashing-instructions.html
And I plan on building this flaching setup