I have integrated Anthony Robbin's "Time of Your Life" (TOYL) approaches with GTD quite successfully. The reason I am telling you this is that TOYL has different categories for things as you are describing. First and foremost, small projects that are comprised of a handful of next actions and can usually be done within a week are called RPM Blocks. This stands for Rapid Planning Method. Each RPM block is comprised of a result/outcome, purpose, and an action plan that is the actual next actions necessary to achieve the stated outcome. A project is a much larger entity, and may take weeks and even months to complete. A project is comprised of many single next actions, and many RPM blocks. One could also use the term mega-project for those huge projects that span a year and may have milestone events, multiple outcomes, etc. I think this process would help you out. The small projects within your main project would actually be RPM blocks, all for the purpose of achieving the project outcome down the line. But each RPM block has its own outcome and associated next actions.
Let me know if you need additional information as to how I have setup Outlook in Office 2003 to have TOYL and GTD working togther.