I haven't looked at this yet, but it is quite intriguing.
"Want to play with RSS feeds? Try xFruits, where, according to tech enthusiast Steve Rubel, you can "teach your feeds all kinds of new tricks."
He's not kidding around, either: you can create a PDF file from an RSS feed, send an OPML to your mobile, aggregate, and lots more. I played with it a little bit and was suitably impressed by all the options; it looks like they're even adding the option to create RSS feeds for your desktop files soon. â_" Wendy BoswellxFruits [via MicroPersuasion]" (from: Mash up RSS feeds with xFruits)
Oh... Why haven't I looked yet? Well ever since xFruits was mentioned on LifeHacker, it has been unable to be reached. The server is probably getting overwhelmed by loving interest like mine.
I say "server" singular? I am just assuming that we are talking about a single server. But even if that's not the case, the fact that the service is unavailable right now says something about how hard it is to build a scalable web service, especially if you are giving it away for free. It is why it's nice to see Yahoo, Google and Amazon publishing services.