Do you mind telling me about some projects in those fields(health specially)?. I'm learning about data mining/machine learning and I'd love to know how this fields are applied to solve important problems and what I can do to help.
don't have specific projects on a list that fits you, but I am sure there are projects out there which needs you help, both projects where you can volunteer or where you can get a job. For a start you could check out our list of health and IT projects in our system, for organisations which work in this area.
Four years ago I was telling people in a session about water and development aid that they should use modern IT and web tools to do their work more effectively. As a result I ended up talking to Jeroen van der Sommen, now our chairman, and we decided to start Akvo.org to provide those tools. There is a huge need for IT tools in humanitarian aid and development work. You could be working on that if you are interested.