headstak is a stack-based task list. Before you start a task, or when you are interrupted while working on a task, you push the current job onto a stack. When the interruption finishes, or when the task is complete, you pop it from the stack - leaving you facing the job you were working on beforehand at the top of the stack. Run it and it should appear on your status bar as a little stack of stuff on a head. It is activated with the Control-Command-0 global hotkey.