GTD is a collection of relatively simple tactics for coping with, prioritizing, and organizing the things you want to do. Many of the methods relate to organizing your own projects, using a handful of context-based to-do lists (e.g. a list of things to do at the office, at home, while waiting in line, etc). These lists consist of simple tasks. Those tasks are, in turn, derived from another list, of “projects” – things that require more than one task, which can be anything from planning dinner to writing a novel to helping your kid apply to university.

I have never seen next actions mentioned like this: tasks that are derived from another list, a list called projects. The thing I like about OmniFocus (and TaskPaper) is that projects are outline headings, and next actions are simple rows. It naturally blends the two together.