AlfredQRCode is an Alfred extension that generate QR Code. It's based on the QSQRCode plugin for QuickSilver, which use libqrencode for QR Code generation.
Just fire up Alfred with the keyword qr, followed by the text you want to process. AlfredQRCode also accept empty argument, if you skip the argument, then AlfredQRCode will try to grab input from system clipboard. You can assign it a global hotkey in Alfred to quickly generate QR Code from copied content.