XawTV is a simple Xaw-based TV program which uses the bttv driver or video4linux. It also contains various command-line utilities for grabbing images and AVI movies, tuning in TV stations, etc.
NIASH's Test Tool is a prototype driver for scanners based in NIASH chipsets (HP Scanjet 3300c, 3400c, 4300c, and Agfa Snapscan Touch). It supports scanning (at fixed DPI) and experimental calibration. It can also be integrated in SANE as a backend.
An interactive designer for Celtic knots.
A simple chess clock to track time in real-life games.