On the site I'm building, users can create tutorials. I want the users to be able to create tutorials on as many  subjects as possible, but still have some preset categories. What's the best way to select these categories?The reason I don't just let users add keywords, and use these for categorization, is because users gain experience points in a certain subject when their tutorial is liked by someone, and in a similar way the Stack Exchange network does, create communities around these subjects. I will give visiters the possibility to suggest new categories.here are the categories that I'm thinking of at the moment:healthgardeningcookingtechnologyscience & mathmusicvisual art
how to select categories for user generated content site?
content;navigation
Why don't you simply use a dropdown list? In the form where they can put the text for their tutorial, you can put this list so they can choose between the category you want.