You've seen a QR code, you just may not have known what it was for or what it was called. For a bit more detail than you probably want, you can head to WikiPedia for all sorts of information about QR codes.
Basically a QR code is a two-dimensional barcode that can contain text. Where this ties in to ProofBuddy is that you can make a barcode containing a web address. So for those of you that hand out cards with your proofing web address at weddings and events you might want to consider including a QR code on your card. That way your clients can just scan the code and go directly to your site.
If you're going to include a QR code on your handouts at events you might want to consider using the ?p parameter as part of the web address. For example, if you have an album with a passcode "123" and your web address is www.bobsproofs.com, you can use the web address http://www.bobsproofs.com/index.php?p=123 and they will be logged in automatically.
Want to create your own? Trying to find software to build a QR code for this post I came across dozens of sites to either create a code or download code to do it. Thanks to the Google Chart API we can embed code to allow you to create a QR code for your site right here.
Enter your web address, including the leading http://, into the text box and press the button.