I discovered QRCodes at 11870.com where they are using them on a Marketing Campaign. There is nice article in Spanish which explains what they are.Also there is another post from a spanish blog which relates first introduction of an occidental guys to it.
For your benefit, I include its automatic translations to English
For our non-Spanish readers I will do a summary:
From 2000 at Japan all magazines and products have started to use QRCode, a version of the two-dimensional code bar for Kanji characters, which is readable with the use of a mobile camera: Simply making a photo is enough for saving the information inside of the mobile device.Companies like McDonalds use them to inform about ingredients or nutritional facts, or MoviStar offering discounts. At Barcelona, they are using them for providing tourist information on the sightseeing points to Japanese tourists.
It is a technology designed for the warehourse but it is mainly target now a mass-consumer products.
How to read a QRCode?
Reading software is available for many mobile manufacturers such as Nokia or from companies specialized in this technologies such as i-Nigma or Kaywa. Nokia provide a page which explain which readers are compatible with each of its phones and which phones have Nokia barcode reader already preinstalled on your device.
This page provide very good information about the applications which support the most common phones.
For iphone users, there is a open source project which provide a reader application called QRDecode, obviously it is only available for hijacked phones on version 1.x, and for 2.x users. Unfortunately, I am not aware. Please, comments welcome. There is a page which explains how to install it with the installer.
How to produce a QRCode?
Nokia has a page where you can produce through a web application which can help to play around a little bit in order to understand all the possibilities.
The first thing we notice is that Nokia recommends us not to exceed 60 characters of text, as mobile code starts getting too complex for camera phones to handle.
Kaywa has also its own application to create this QRCodes from URL, Texts, Phone Number and SMS.
Well, folks that is enough for today. Next chapter we will see how to create programmatically QRCode from XML through J2EE or Ruby on Rails.