A friend sent me a link the other day to a website called galaxy Zoo . Its purpose is to categorize a million galaxies. They're split into two main groups elliptical and spiral. Irregulars and Lenticulars are not included, the former being too faint and the second are classed as elliptical. What you do is is register with the site then progress to identify the different types of galaxies that they show you. Before you get to identify the galaxies, there is a test to make sure you know your galaxies. Its free to join so if you've got a few free hours, have a go.