The Kanban technique (看板)

A Kanban ("signboard" or "billboard" in Japanese) is like a 2D todo list. You write each task on an individual paper. It has been created to organise small projects for small teams, but can be used even if you are alone with multiple projects.

Each column is dedicated to a specific state of the tasks: Todo, Testing, In progress, Done, etc. Once a task has been done, you just have to move the sticky paper to another column!