Clearspring Technologies is the parent company of AddThis, a widget that enables website visitors to share content. Clearspring has raised $20 million in a fourth round of funding, led by Institutional Venture Partners. Former AOL executive and director Ted Leonsis is the company’s chairman and Hooman Radfar is CEO. AddThis is installed on over 9 million websites and is used over 1 billion times per month. [MarketWire]

Clearspring Technologies is a widget company that generates revenue through a Widget Ad Network.  The company announced this morning that they have acquired AddThis.  AddThis is a bookmarking button that appears alongside many blog and online news publications.  AddThis also appears on the homepage of Pulse 2.0 at the bottom left where it says “Bookmark.”  AddThis has about 200 million users and 300,000 publishers.  Clearspring aims to become the leading content sharing widget. 

I first wrote about AddThis in October 2006.  AddThis is based in Princeton, New Jersey.  AddThis is also used on sites like TIME Magazine, Oracle, EW, Topix, Lonely Planet, PGA Tour, Tower Records, FOX, ABC, CBS, America Idol, Glamour, and WebMD.  The AddThis button is loaded 20 billion times per month.

Dom Vonarburg is the Founder and CEO of AddThis.  The company officially launched at DEMO 2006. Although the acquisition price is not known, AllThingsD predicts that the amount was for a few million and some form of stock swap.  AddThis’ main competition is ShareTHis and Del.icio.us.  Clearspring makes about $10 million in revenue per year and believes that they can use AddThis for advertising purposes and data analytics.

Clearspring also has about $35 million in funding since they started in 2004.  Investors in Clearspring include Steve Case, and New Enteprise Associates.