I'm looking for volunteers to join an Australian team which uses BOINC to help solve maths problems, health issues, space exploration and many other exciting topics. This is a global volunteer system developed by the Berkeley University.
BOINC stands for Berkeley Open Infrastructure Network Computing. You can read about it here.
All you need is a PC or even an Android based system. It runs on many platforms.
If you have an interest in space, you can chose a space project. For example - Einstein@Home.
"Einstein@Home uses your computer's idle time to search for weak astrophysical signals from spinning neutron stars (often called pulsars) using data from the LIGO gravitational-wave detectors, the Arecibo radio telescope, and the Fermi gamma-ray satellite. Einstein@Home volunteers have already discovered about fifty new neutron stars, and we hope to find many more."
Or if solving world health issues lights your fire then perhaps choose the World Wide Community Grid which was set up by IBM in 2004.
If you are interested in joining an Australian team and climb the ranks, check out the Facebook page and get in touch. They also have a forum where there is plenty of friendly help. (I disclose I am a team member)