How to: different wordpress blogs, one feed?

I want to have 4 or 5 different wordpress based blogs and I want them all to feed into one. I already have several domain names and a host. But, what I need to know how to do is create 4 separate blogs, each with there own URL and look, that all feed into one master feed. That master feed will serve as a hub from which you can link to all the other blogs. I don’t think using tags or categories will work because each blog/topic needs to have its own look and mechanics, but I could be wrong. Any info on how to get started or links to somewhere I could find this info would be helpful.