In Android and the Mac client you have an option in the "Next" panel for viewing All next tasks, or only one at a time.

This feature doesn't seem to be available in the web. This is (as far as I can tell) the closest thing that DoIt.im has to a managed "Next Actions" list from GTD. While not ideal, it is better than the default listing in next, which is to list all available tasks that do not fall into Scheduled, Someday, or Waiting.

Barring a proper GTD Next Actions list, I would like to see the "One" option added to the web interface.