Previously I had posted few articles here about QR code, such as what is QR code, how to read it, how to create custom QR Code and difference between classic Bar code and QR Code. If you are looking for a free, custom QR code generator with advanced features, just try Unitag online generator.
With Unitag, you can generate colorful, attractive custom QR code for any of your needs (text, me card, email, sms, website, etc) and download as PNG file. You can customize your QR code with colors, gradient and embed your own logo image for branding purpose.
However, take care while creating color gradient QR code. Contrast between light and dark areas must be strong enough; otherwise, it will not be readable.
Moreover, overlaying a logo might make the QR code unreadable. So, check it yourself and make changes still it works using your own reader.
NB: Some readers cannot decode inverted (white on black) QR codes.
Unitag is a free service; however, the premium service offers advance features like SVG export, creation history, batch generation, analytics, etc. Try Unitag for free.