Another code is Data Matrix (http://en.wikipedia.org/wiki/Data_Matrix) which is now having some backup from both the US Govt and the electronic industry which is planning to add extra information on top of chips and small components: these would be read by automatic assembly machines for a more reliable and foolproof assembly of boards.
PC and mobile phones encoders/decoders are available for Datamatrix as well, but I went for QR code and basta ! No, actually I tried some free Datamatrix decoders and proved less reliable, on my phone at lest, than the QR decoder I am showing here.
"QR Code is trademarked by Denso Wave, inc. as stated in Denso Wave's" this is what can be read on Wikipedia and on Denso Wave's homesite but we can read also that (http://www.denso-wave.com/qrcode/microqr-e.html) "QR Code is open in the sense that the specification of QR Code is disclosed and that the patent right owned by Denso Wave is not exercised.".
And that's great because this opens to a great deal of opportunities.
...Follow me then and you'll have Y2010 business cards also.
Note (01/02/08) :
Jaxo System's web address has moved to http://www.jaxo-systems.com (thank you, jackOjack)
Step 1: Parts Needed
Some text to 2D-encode (and worth to decode !).
A PC with a Web browser and Java VM : Windows or Linux doesn't matter for the encoding process.
The decoder applet for your camera-equipped mobile (if you want to decode also, I want).
The text for me will be https://www.instructables.com and http://www.5volt.eu , the latter being the place where I post my projects I can't make an Instructable. Both worth to me to encode and print on stickers, business cards and T-shirts.
The PC can be any, equipped with a web browser and Java.
Jaxo Systems ( http://www.jaxo-systems.com/home ) makes software for image processing also and provide decoding Java applications for mobile phones and PCs to acquire and decode various bar codes (2D included) and free to download.
In their homepage you can encode your text and save the 2D representation as a graphic file ready for print.
You can also download the jar file to execute as a stand alone application.
Use is granted by Jaxo Systems for personal use only, as stated in their homepage.
Below is a roundup of addresses found by readers and posted in comments.
Many of them have downloads for mobile phones, some others have directions for others sites also.
http://www.drhu.org/ (suffering HD failure as of 31/01/08)
Step 2: Encode
Go to http://www.jaxo-systems.com/home
In the Java applet click on file->new to start from scratch. Type or paste your text in the message window. While you type the 2D encoding while appear on the left in the preview panel.
When you're done select file->save as...
The saved image can now be resized and incorporated in logos or prepared to be printed on stickers, flyers, business cards or T-shirts along your logo or, say, the instructable robot.
That's not it. The applet gives much more.
Infact, very interesting an option allows the user to include details like mobile phone numbers and domain names to make them directly accessible by the phone and save them in the telephone directory or send an SMS to or open the web page directly on the phone without typing anything. No typing errors!
Too bad the applet for my phone (Sony Ericsson K750) apparently do not control the macro mode so closeup pictures of 2D logos on business cards are too out of focus to be decoded. Hopefully a newer release of the java applet for my phone will solve the problem.
Anyways, just shoot with the phone a QR-encoded business card and a few clicks away contact details will be in the directory.
Step 3: Decode
Now start the mobile reader on your phone, point the camera to the code and shoot the photo. You'll be likely required to permit the camera to take pictures, just click ok...
License plates like the ones seen on "The 5th element" and based on regular 1D bar codes are surpassed already. Think at the contacts that could be sent through dynamic arrays of LEDs or LCD TV screens, all without the need of radiofrequency.
What I described here is a suite of applications which were already in the minds of the designers of the 2D codes, I did not invent anything.
Possibly someone already prints T-shirts and business cards like the ones described here : I just wanted to make a roundup of these design opportunities for the community to enjoy.