When you’re done playing with LEDs, motors,switches etc the next thing to do is connecting a 16×2 alphanumeric LCD module. The LCD modules are affordable (less than $10) and effortless to interface to the Raspberry Pi. They have 16 data pins but we would be using only 6 pins.
Almost all 16×2 LCD available in the market are based on Hitachi HD44780 LCD controller. This permits you to purchase nearly any unit and make sure its determined to work in same way as all others.There are loads to browse on eBay.
Step 1: Circuit
The circuit consists of a 8 bit I2C port expander IC named PCF8574. HD44780 is interfaced with Raspberrypi via PCF8574.
For the main circuit & schematic please visit my blog for more info- http://www.rpiblog.com/2012/07/interfacing-16×2-lcd-with-raspberry-pi.html
For more detail: Connecting 16×2 LCD to Raspberry Pi