Show a Category Specific Info Box

There are multiple ways to print content on the front end. The “best” way depends on the details of the project and your description is very superficial.

The option I can think of are:

1. Just edit the appropriate theme template to use has_category
   to display your links to the category URLs
2. Do the same as above but use a filter on the_content to avoid
   editing the template files. Good if you may use multiple themes, not
   just one, or if this needs to be portable to other sites.
3. Use a widget. This can be a bit trickier but I don’t know about
   “messy”.

Which is “best”? Or better than a widget? No idea. That depends on what you need to do, where you need to place the content, etc.