In my implementation of GTD, I don't have separate lists of projects and next actions. Instead, I simply annotate each project with a note of what its next action is. I use my e-mail (stored in Mozilla Thunderbird) to keep track of some of my projects. Unfortunately, this mail client doesn't make it easy to annotate messages that I have received from someone else. Sometimes, I would like to use a message from someone else as the basis for a project description and then annotate it with the next action, location of reference materials, et cetera. In addition, it would be really nice to be able to sync messages that I'm using this way with my PalmOS todo list.
So I've been thinking a lot about the (non)portability of documents: how awkward it can be to move a piece of information from one place to another. It almost seems as though we've imported the restrictions of a paper-based environment into the electronic one. In the electronic environment, a document can be filed in two places at once. In the electronic environment, information stored in one medium (a mail client) can be yanked into another (a todo list). Partly because of attempts by software companies to control data formats and partly because people haven't yet thought of what might be, our tools aren't yet what we really want.