ReadWriteWeb

Superfeedr, a service that transforms a wide variety of feeds into normalized XMPP or Pubsubhubbub format, announced a seed round of funding from some very high-profile backers this morning. Betaworks, backers of Twitter, Bit.ly, Tweetdeck, Twitterfeed, Tumblr and more, and Mark Cuban, have invested in Superfeedr's parent company Notifixious.

Superfeedr offers services to both publishers and subscribers. Current marque users include SixApart, Adobe, Twitterfeed and Posterous. Notifixious founder Julien Genestoux first met Betaworks CEO John Borthwick at our event last month, the ReadWrite Real-Time Web Summit.

There's a seemingly infinite list of startup companies based on adding one form of value or another on top of Twitter. One called TipJoy closed its doors this week, despite a remarkable set of blessings that thousands of developers throughout the Twitter ecosystem would be wildly jealous of.

TipJoy offered a service that would let people pay small amounts of money as tips for online content, with the transaction being processed via messaging on Twitter. That wasn't the only way TipJoy worked, but the company was very closely tied to Twitter.