The Adafruit LCD backpacks reduce the number of pins needed to connect to an LCD. LCDs are a fun and easy way to have your microcontroller project talk back to you.
Darn that Adafruit! We had been stirring the pot on a similar project, because it's just so common-sense to do. But they beat us to the punch, and we'll carry their product instead.
The wonderful idea is a simple backpack module that is installable to most character LCD units, and make it easy to use with a minimum of communication lines. This backpack uses simple i2c and SPI input/output expanders to reduce the number of I/O lines to as few as 2 (using I2C), and Adafruit has even written an easy-to-use Arduino library that is backwards compatible with projects using the '6 pin' wiring.
This backpack will work with any 'standard' character LCD, from 8x1 to 40x4 sizes! As long as they have a 16-pin single-line connection header at the top.
For advanced users, this project can be used for general purpose I/O expansion, the MCP23008 has 8 i/o pins (7 are connected) with optional pull-ups, the SPI 74HC595 has 7 connected outputs.