Most everyone is familiar with the 1-dimensional barcode. It's that little strip of black bars that we find on ID cards and UPC labels at the store. This label is designed to be easily read by a computer for fast data entry. Think of how slow your grocery shopping would be if the cashier had to hand input the UPC numbers in for every item in your cart! (Interestingly enough, with a bit of work you can teach yourself to read 1-dimension barcodes)
2-d barcodes are the same in principle- a pattern designed for computers to easily read. The advantage of a 2-d barcode over a 1-d barcode is data density. While a normal barcode can usually holds around 10 characters, some 2-d barcodes can hold upwards of 3000 characters in a similar physical space.
2-d barcodes are all around you. Look at your mail or even on the back of your driver's license! Some banks use these codes to track documents, and many electronics manufactuers are moving from 1-d barcode to 2-d barcode for serial number recognition.
One great thing is that with the right kind of cell phone and the right software, you can read these codes!
In Japan, virtually all cell phones come with some kind of 2-d barcode reader. It's very popular to have a 2-d barcode associated with an advertisement in Japan.Huge towering billboards will display a code, which you can take a picture of with your camera on your phone. Your phone will then translate the barcode into useful data. This data can cover everything from coupons to DPS directions to a location.
Here in the States, the trend hasn't caught on quite like it has in Japan, but it's taking a much different route. Instead of taking manifesting itself on advertisements, individuals are using it as a sort of identification tag. You can make a code with a link to your website or blog, then easily put it on your business card, on a poster, or even on a scarf! You can use it to pass notes back and forth with a friend in a public place, as a scavenger hunt marker, or a million unique and fun ways.
So What do you need to get started? First you need to pick a barcode format. There are many many different standards for 2-d barcodes, but I'll focus on QR-Codes and the Datamatrix code. Both of these standards are in the public domain, easy to make, and usually easy to find software for phones to read.
Kawya.com offers a great QR code generator and a datamatrix generator. You can enter in whatever text you want, then you can save and print your barcode.
Some of the more popualar readers are Kawya.com's, BeeTagg's, and Here is a list of other bar-code reading apps for your phones. Kaywa and Beetag work with both QR-code and Datamatrix, but Scanlife only works with Datamatrix. You can install the software straight to your phone (if you have a dataplan) by visiting these sites in your mobile browser. Otherwise you can save the install files on your desktop computer and move them to your phone.
There are always software and hardware limitations, but as the technology gets better, more and more people can easily adopt the technology. So whether you want to use it to keep track of stock in your new business, or just to have fun with your friends, go out and spread the word about 2-d barcodes!