Celebrate Citizen Science September with Zooniverse, a collection of projects in space, climate, nature, and humanities. Registration is required but free.
Galaxy Zoo lets students view Hubble photographs to classify galaxies by shape and other features with the aid of a visual taxonomy. The site explains how galaxies form, has a catalog of images, links to published papers, and lets visitors create words with images of galaxies using Galaxy Writer.
Moon Zoo has a short video demonstrating a Crater Survey interface. Participants mark, size, and look for boulders in images of craters.
With Solar Storm Watch, students use interactive diagrams to learn out about the Sun and spacecraft monitoring how solar storms affect conditions in space and on Earth.
Planet Hunters lets users search for planets orbiting other stars.
The Milky Way Project asks users to find and draw circles on infrared image data from the Spitzer Space Telescope. A tutorial explains the process of identifying and marking bubbles and other objects of interest.
With Old Weather volunteers contribute to climate model projections by recovering worldwide weather observations made by Royal Navy ships around the time of World War I.
WhaleFM participants categorize Orca sounds to help scientists understand what whales are saying.
Ancient Lives is a project to study the lives of Ancient Greeks by studying the Oxyrhynchus collection.
Teachers can find resources for the classroom at Education.
All projects require careful attention and are best for grades 6-12.