Feed Mix
Feed Mix is an RSS editor, which is powerful enough for RSS gurus yet refreshingly easy for RSS first timers. It lets you create, edit and publish the unlimited number of RSS feeds and podcasts. Unique to Feed Mix is its ability to create a new RSS feed or a podcast from several existing feeds. ... You should specify which news from the selected RSS feeds you would like to see in your new RSS feed, and all the mixing job is done by Feed Mix. ... You click on the "New Project" button to create a new RSS feed, select the source RSS feeds and add them to Feed Mix.
http://www.extralabs.net/FeedMixSetup.exe - 2Mb - Download - Screenshot