This is a POS (point-of-sale) system I wrote for a Chinese restaurant. The client ended up pulling out on the contract, after it was essentially complete, so I've decided to license it under the GPL and throw it up here in case anybody wants to play with it. I don't expect to touch it again personally, though I'd be very interested to know if you actually find it useful in some way (if so, drop me a line).
It has an ncurses interface and uses a PostgreSQL database backend. Features include a searchable and scrollable menu, multiple item sizes, persistent customer records, and integrated caller ID (if you hook it up to a modem, it'll detect incoming calls and start creating a new order for that customer, if known). It was designed to be used with something like zhcon to get support for Chinese characters, though that is not required.
The client for which this application was originally developed had incredibly specific and strict requirements on the user interface, largely focused on removing as many keystrokes as humanly possible (which, IMHO, makes for exceedingly cryptic and occasionally inconsistent UI behavior).
Anyway, here's a tarball of the source.