job search - How to make leaving a PhD program seem like a positive thing on a resume

I have a feeling this question has been posted before, but I wanted to ask as my situation is slightly different. I've recently decided to leave my PhD program in the social sciences in order to look for work. I've basically come to the conclusion after completing 3 full years, courses, and fieldwork that I don't want to be an academic but would rather put my skills to use with NGOs, non-profits, or the public sector. In many ways, the last hurdle of the PhD (i.e. writing the dissertation) seemed more like a barrier to what I wanted to do, rather than something that would bring me closer to it. I left because I wanted to go in a new direction, not because I wasn't sure that I was capable of finishing.

Anyways, my main concern right now is how to present this discrepancy on my resume. As I've been a TA and doing research projects since getting my MA, I've decided to list my years as a TA, and the rest under the position of "Researcher." I figure that the situation is a little too complex to really explain in a resume or cover letter, and that most employers will be able to read between the lines that I was probably in a PhD program. I've basically been marketing myself on my resumes/cover letters as a "researcher" with lots of research projects under my belt, without specifically stating under the "education" section that I have a partially finished PhD. My motivation behind the "researcher" title is that during my graduate studies I designed, proposed and carried out individual research on a number of projects.

I guess I should qualify this by mentioning that my PhD studies were in the social sciences, and there seems to be a bit more leeway in terms of describing what we do. All of my dissertation research was funded by a fellowship, and all of my various other research projects (where I wasn't principal investigator) were the result of competitions funded by grants. I have always designed my own research projects, which is why I didn't think it was a bad idea to go with "researcher", and my references could verify that.

It looks like this title would be a little confusing given the circumstances, so I think I'm going to use "Graduate Student Researcher", "PhD Researcher" or something similar in the future. I guess this seems like it gives a more accurate representation of what kinds of things I was doing. I figure that the 4 years of MA/PhD work on research projects gives me (and any other former graduate student) skills that are valid to most employers. I just want to be able to address this discrepancy honestly and enthusiastically in an interview, rather than clumsily addressing it in a cover letter/resume. What do you guys think? Is this the right strategy to take?