The "PCF8574" chip is an I2C I/O expander that free some of your Arduino pins by controlling them over I2C. The PCF8574 is directly powered by the 5v rail of your arduino and let you control 8 I/O ...

Library for PCF8574 Breakout Board by Testato on ArduinoForum, based on code from Mario H. You can see in the picture I2C_LCD_Breakoutboard.jpg the board compatible with this library. Without solder ...