Habrahabr.ru runs an excellent post (in Russian, but with lots of pictures), showcasing some really cool designer QR codes. I’ve tried scanning them with my Android mobile and not all of them worked, but quite a few did. Like this one, for example.
A while ago, I was looking for a QR code generator that would embed a custom image into the result. Back then I didn’t find one and had to do things the other way. Now, there is one – QR Art. Here is an example, using my picture from the about page.