Yahoo! Pipes is a sophisticated composition tool for manipulating RSS feeds. With it, you can filter, sort, translate and geocode your RSS feeds into perfection. For the simpler task of just aggregating multiple feeds into a single RSS feed, there’s Feedstitch. Both tools are free, and allow you to use your resulting RSS feeds however you wish.
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If I understand your question correctly, you are interested in using an RSS aggregator for video SEO? I don’t think I can help with that, but as far as your free/Mac question, the answer is yes. Yahoo! Pipes is free and it runs in a browser, so it is platform agnostic.
What will allow me video to get to the top of Google using rss feed aggregator. Which one and is it free for Mac