Screen Marker allows you to write and draw directly on your desktop and above all of your opened applications. You can use it to highlight areas you want people to notice before taking a screenshot, draw on "smartboard" in classroom settings or just doodle away during those "important" meetings.
Screen Marker was designed to be simple to use but robust enough for your average doodling needs.
** Note - Screen Marker is not designed to work with individual applications like Power Point. Screen Marker is utility to draw on your desktop, not inside individual applications.