Visualead is a great QR generator that combines an image with QR codes.  I really encourage classrooms to use QR codes for certain lessons.  I really like the idea of accessing information quickly especially within the classroom.  The app that I use on my smartphone and iPad is Scan.  This seems to be one of the best, free QR readers available.  I think for classroom use the FREE version of Visualead works just fine.

An overview video about Visualead is embedded below.

Below are all of my created Visualead QR codes