11 aggregators of feeds on the wall
Swamp Tech
"Take one down, pass it around," one less feed aggregator on the web.  It seems several once-popular sites that combine feeds (aka feed aggregators, blenders, combiners, mergers, mixers, multiple feed merge) are no more. These sites combine 2 or more syndicated (RSS / ATOM) feeds into a single feed.  This can be desired if you want a single source for multiple sites or have limited space for displaying syndicated content.
Several feed aggregators discontinued their free feed aggregation services, including RSS Mixer and FEEDblendr, for various reasons including RSS spam and cost of operations.  Several others, including ChimpFeedr, Feed Informer, and Yahoo Pipes, continue to provide this free server.  In addition to combining feeds, some of these hosted services provide the ability to filter stories based on keywords in addition to setting the number of items to display in the feed and the maximum number of items per source feed.
Former feed aggregators that are no more:
  • BlastFeed (http://www.blastfeed.com/)
  • FEEDblendr (http://www.feedblendr.com)
  • FEEDcombine (http://www.feedcombine.co.uk) - now provides source upon request to host your own feed aggregators
  • FeedMingle (http://www.feedmingle.com)
  • RSS Mixer (http://www.rssmixer.com/)
  • xFruits (http://www.xfruits.com)
However, several remain:
And some that don't work (but haven't thrown in the towel yet):
  • FeedRoll (http://www.feedroll.com/)
  • Feedbite (http://www.feedbite.com/)