Up until the late 2000's, pretty much all information on neighbouring galaxies was compiled by a handful of experts using the Hubble telescope and millions of dollars worth of equipment. While their input was frankly monumental, this was a largely impractical way of gathering information. It just seems like a waste for such a small number of people to have the power to provide such information.
In 2007, the first Galaxy Zoo was launched; one of a number of Zooniverse projects designed to allow pretty much anyone with an interest in space (and access to a high-powered telescope) to report and file hundreds of new galaxies. This project was created with the interest of dividing up galaxies with "spiral" and "elliptical" motifs, and it worked well! Many new galaxies were discovered and categorized, but many others were not, since there were only two options which didn't allow for the description of mixed elliptical and spiral.
Two years later, the Galaxy Zoo 2 project was launched following the success of the first one. A new categorization system was introduced which allows users to report other shapes and oddities, in fact it literally asked you "is there anything odd?". You were also able to report what colour the galaxy was, and therefore where it is with respect to the milky way. This was overall a much more sophisticated system, it even had an algorithm to report population bias, ie: which features were reported by the most people.
The Zooniverse team has now made the classifications and images of both Galaxy Zoo projects public, including images, classification, and even population bias. A paper has also been published.
The team is now working on a new project, Galaxy Zoo Quench, which allows "citizen scientists" to get involved in the classification of new galaxies discovered using the Hubble telescope, only this time they're allowing users to input theories about how they think the galaxies formed.
If you've got a keen interest in astronomy and astrophysics, the data analysis stage is still open! No prior knowledge required.