Someone already mentioned Blogs Automater, which is a great tool for using sponsor RSS feeds as it will not only aggregate the feeds but allow you to organize them in many different manners. It also will do a search / replace on keywords you determine basically giving it the ability to morph the feeds to help with duplicate content.
If your looking for a tool to control multiple blogs that can also do feed aggregation, their is
Blog Organizer
I'd suggest you take a look at booth scripts to figure out which one is the best for what your trying to accomplish.