I'm playing with Lists, and it does most of what I want.
I can create an HTML/text field and use the 'add link' edit option to add a title and url for external links. This then displays a field with a clickable title, taking the user to the linked site. This works fine, but I feel this will be beyond most of my users.
So, I created Business Process to create an HTML tag once the user had entered two fields - one for Title and one for the url.