You may already know that most blog software has RSS capability built in. Providing yours has and the sponsors you want to use produce more or less valid feeds, those two sites should be fairly easy to deal with.
The other two are more problematic in that unless you can pull
all the feeds off one of your blogs, you will need an aggregator such as
Rapid Feeds' MySite. Its job is to combine and sort the feeds from multiple sources.
Even if you can pull a single feed to your other sites, IMO
RSS2HTML (from the same company) would be a much simpler and more effective solution.