"QR Codes are barcodes that contain digital information such as URLS that can be read by camera phones. "
This is my QR code for my Profilactic Mashup rss link. (Profilactic allows me to mash my digg,twitter,netflix,livejournal, flickr, and any RSS into one feed you can read in your RSS aggregator)
The little blocks on the corners help the software lock on. This one will create an SMS message with an embedded phone number and if you press send, sms me that i'm a dirty whore.
I used the QR code generator at http://qrcode.kaywa.com/ and the software from i-nigma that you can download to lots of windows phones and seems to be particularly supported by Nokia.
In my research I found out that Pet Shop Boys embeds QR codes in their Integral Video and have even included a PDF on their website so you can remix your own QR code video and then upload to a youtube group. Those PSB are always on the bleeding edges of technology and music. All of the links are subversive in the video. Links to Biometric data collected by the UK govt, blacklisted news sites, statewatch, bbc politics, etc.
Why is this useful? Well you dont have to tap in long urls with them. You could use them for bridal registries. You could email them to friends so they dont have to key in all your contact info. The possibilities are many, I guess. It's basically a scanner software on your camera phone to read em
This final one is my contact info. It will send you an sms and ask you if you want to add to contacts =]
I used the i-nigma one for this one cuz the kaywa one didnt do the contact info one properly.