Does your mobile device/phone read 2D barcodes? There are half a dozen free iPhone apps for reading Datamatrix or QR codes and then processing them in some way. For instance, if you're encoding a URL like the one to my blog (https://the0phrastus.typepad.com) the app will decode it and pass it along to the browser (Safari if you're on an iPhone).
Get yours here. (links to Nokia site).
Here's the QR code for the same address: