On the Zend Developer Zone, a new tutorial has been posted that anyone looking to "blend feeds" might want to take a look at. It's a guide to using the Zend_Feed component of the Zend Framework to combine the contents of multiple RSS feeds.
As part of my playing around with the Zend Framework, I've decided to make this merged RSS feed using the Zend_Feed component. Actually at the end I've realized that this merged feed idea is quite useless, but at least this post came out of it :-)
He developed it originally as a way to combine his twitter and blog feeds into one thing to provide the latest updates to readers from both in one simple place. He shows how to take in the two feeds, each in its own feed object and merge them into one array. This array is then pushed back out to the visitor an the RSS format (thanks to Zend_Feed_Rss).