I use the command-line utility qrencode, it's available in most package managers.

https://github.com/fukuchi/libqrencode

If it is just for one-off stuff these days most browsers let you share links in QR code format, when you pull up the qrcode you can modify the text box as you see fit

If looking to customize qr codes, toss in "styled qr code" into GitHub and I'm sure a few WebApps will pop up