I have a lightning component that I would like to load in a dialog box after a ui:button has been pressed. Are there any existing Lightning components for doing pop up dialogs or should I be looking at a 3rd party js library for that kind of functionality? 

I don't see anything in the component reference that fits what I'm trying to do. The only thing that might fit the bill is ui:message but it seems like it's intended for simple informational messages.