This simple Flash-based Web app lets you encode arbitrary text, a URL, phone number, VCard, or even a WiFi access key for Android devices. You pick the data type you wish to encode, and fill in the data you want the QR code to contain. Next, just click the large Generate button, and your QR code will pop on the screen, ready to be scanned by any smartphone.
While a QR code can contain lots of information, it was not designed to be pretty or eye-catching. Half of the QR Hacker interface is dedicated to the task of making your QR code fancier without breaking it. You can round off its pixels, change the background color (or even pick a photo), or change the foreground color. But the feature that really blew me away was the ability to embed a photo or logo right into the QR code: I was able to import the PCWorld logo and place it in the middle of my QR code, and even delete some of the pixels around it to make room for the logo, all without breaking the code. My Android phone kept on recognizing the code instantly, PCWorld logo and all. Impressive. QR Hacker then let me save the QR code either as an image file (PNG) or as a PDF document. The site will soon have a Web Shop for buying merchandise with your code printed on it.
QR Hacker also contains a gallery of codes users created using the application. While many are beautiful, you should exercise reasonable care while scanning them: QR codes can contain URLs leading to risky websites. Just like you wouldn't click any random link on the Web, you shouldn't randomly scan any barcode shown on the QR Hacker website. Still, the showcase serves for seeing what can be done with QR Hacker, and I must admit it features some of the most striking QR codes I've seen yet.