FacileThings
New GTD Project Management in FacileThings: Personal Kanban
In GTD, most of your projects (by definition, any outcome that needs more than one action step) will be a sequence of actions to be performed one after the other to achieve the end result. In such projects, FacileThings shows you only the very first next action of each project in the Next Actions list. And when you complete it, the following action shows up automatically. So straightforward.