Has anyone ever set up one site that is essentially an umbrella site that "houses" all your individual sites? So that you can have a business card with one url that a client, etc. can access and then from there can go to any of your individual niches?

What was your experience[s] with doing that? Does it help? Hinder?

While my micro niches are named after my keywords this site could very well have a catchy name, or my name...

So I need the experienced to "set me straight" on what's the thinking on this?

Thanks!
~MaggieB