Beyond that. Here's a bigger example:
Lets say I want to learn PHP. You can't really write a howto on How to Learn PHP since PHP covers so many different things. A howto would be more like How to Validate Forms with PHP.
So for people who are absolutely new to PHP, they could look add themselves under the "I want to learn PHP" category. Inside the category, people could post links, books, ideas, etc on learning PHP.
If this were to become a database driven application, you could add a bunch of extra features to this like 'I graduated the PHP category' and 'I see you're learning PHP, you might also like to learn about Apache'. Stuff like that.