Should I make a splash page or what?

Okay so I’m looking for a plugin that will be able create a page or popup that will show the viewer a sort of menu in which they could pick what they want to see. For example I have different sub domains of my main domain that focuses on different things and I was wondering if I can have some sort of way for when the person lands on my main domain site they just see a menu which leaves the option to view the other categories… I hope this makes sense.