Not sure if I'm going about this the wrong way. I would like to have a menu linked to a category, resources. That would drop down to show other categories that also have posts in common with resources. When I click on these categories, the page would show all posts that have both resources and the category clicked in common.

Does that even make sense?

no it doesn't make sense. there is no term 'resource' in the wordpress vocabulary

you can create menu's with pages and categories, dashboard->appearances->menu

Thanks for pointing out my lack of communication skills

I'm putting some posts in a category called, by me, "resources". These posts are also under other categories such as "books", "videos", "links", etc.

What I would like is to have a menu that shows only the categories that have posts also categorized as "resources". When one of these categories is clicked it would load up a page that shows only the posts that have both resources and the category clicked attached to them.

So if I hovered over the menu named "resources" I would see, among others, "books". When I click on books I am taken to a page that shows only the posts that are categorized as books AND resources.

I am provably going about this the wrong way...

My first inclination is to use the List Category Posts plugin and put the shortcode with attributes to display only posts that in are both categories and displayed how you want them. You are probably going to have to take a bit of time wrapping your head around the shortcode syntax and attributes but I have used it multiple times with success.

You would of course then just put a link to this page in your menu or sidebar.

The link in the post takes you to the plugin instructions.