Joining a Citizen Science Project

Years ago I was a participant in the SETI at Home project, using spare cycles on my PC to help find signals from alien civilizations. That project has wrapped up the public part of its research right now and entered a data analysis phase. But there are many other science projects that ordinary people can participate in. 

There is a wide variety of projects. Some, like Globe at Night and Smoke Sense, rely on direct observation and reporting. The Smithsonian Digital Volunteers project uses volunteers to digitally transcribe documents. If you don't have time or inclination to work directly with observations or data, projects like Folding at Home use the spare cycles of your computer to conduct research or analyse data.