2 feeds together?

["browser1" <browser1@yahoo.com>]

OK here is what I want to do and I cant figure out how to do it.  

I have several different elements I want to include within an rss 
feed.  So is there any way to put 2 or 3 different rss feeds within 
one xml feed?

The purpose would be for aggregating content online to different 
sites. I can do this within a php aggregater but then I cant get it 
out to the other pages on other servers.

The idea is if I can do it in one xml page I can then syndicate the 
single xml feed that includes 2 or three feeds in some combination.

Thanks