A few days back we walked you through creating QR codes via the command line in Ubuntu. Following that post a developer, David Green, put together a GUI front-end for the process, allowing for a more user-friendly experience in generating 2D barcodes.
QR Codes are nifty time-saving shortcuts; sort of like hyperlinks for the real world. Qrencode is a small command-line utitlity that allows you to create your own QR codes (saved as .png image file) for whatever you like - a blog, a secret message - whatever!