Barboek is an application I helped to develop at the students association Demos. It is a fully fledged point-of-sale system, including inventory management and accounting functionality. The main system was built by @pieterpaul, and I originally only worked on the design. Later, I took over development, and finished the system with a bunch of friends. It is now used every day at the students association.
The main interface is optimised for touch interaction, and used through a touch screen mounted behind the bar. Products are split into (customisable) categories, and have one or more associated unit quantities (e.g., glass, pint).
To start a transaction, you can quickly authenticate by scanning an NFC tag that can be linked to an account (alternatively, you can search for an account). This works by running the web app in custom PyQT application that sends NFC token identifier (encrypted) to the web app. Any NFC card can be linked, including your university card, which speeds up the ordering process significantly.
In addition, the system contains many features specifically tailored towards the associations culture. You can add temporary (e.g., one hour) discounts with a countdown, each account has a secondary balance for internal rewards, custom themes can be chosen for activities hosted by sub-associations, and it is possible for members to partially contribute to an order of someone else (i.e., split costs).