I graduated with a Masters of Engineering, concentrating in digital signal processing, in particular medical and audio, almost two years ago. I've always been interested in research, but due to personal circumstances I could never commit a lot of time to working on a research project with a professor, and obviously didn't get a chance to publish anything. Now that I'm more settled and have much more time on my hands, I started getting involved in some open source projects and reading some technical literature (engineering, mathematics) that I couldn't get to before. However, I'd still like to find someone to to collaborate with on a research project who is already established in the field and publishes papers. Part of the reason I want to do that is to be able to eventually apply for a Ph.D. program in a good school, and having publications would be a great thing on my resume.
What I'm trying to find out is how I can work on a research project similar to those graduate students work on as a part of their studies if I'm not a student anymore? Should I contact my old professors from the university? Is it possible to find some "open research" team that accepts collaborators from outside? Do I have to do it on my own (quite frankly I'm not sure I can give myself a good enough quick-start)? In short, I'm willing to volunteer my time in exchange for a possibility of publication in the future. Can I do it, and if yes then how?
The short answer is yes, you can.
There is no need to be in a university, a research lab to work on a research project. There is also no need to have a PhD or any other specific degree/position. This is however somehow unusual. But, there is a bunch of people in industry that publish on a regular basis some serious research work.
If you have no idea of the problem you want to address, or at least a broad domain, this will be even harder. I can only advice you to offer your manpower to people who are established researchers. For that purpose, you can go to seminars, you can maybe, if this is possible where you live, lurk into some graduate lectures, etc. After a while you will be able to talk with people and offer your services. However, the simple way is to work with relatives. For instance, my brother is an entrepreneur, and he wrotes two papers with me (one is published, the other will be soon I hope). Of course, it was simple: I described one of my problem on a sunday lunch at the parents house, He had some ideas, we worked on it...