Listing posts by category for multisite

I am a php programmer and know this is a hard task. I'm wanting to get posts from multisite users via categories. Problem is, the categories are not uniform between blogs. So, I want to do a wildcard search on categories so I can list for example all blogs with posts with the search "*relativity*" as a category. That I imagine will require some intense programming. Do you have something like that or code I could use? Thanks! -David de Hilster, Boca Raton, Florida