Just read on Netanel Jacobsson's blog about Yoono, a collaborative searching, exchanging and information sharing service. The service is employing a unique approach by indexing "web users' bookmarks to overcome problems of language, synonyms and other syntaq quirks."
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Yoono
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Yoono is a free software application you can download which combines for the first time the management and sharing of information. Based on pooling user knowledge, yoono is a collaborative search engine and an innovative communication tool.
With yoono, don’t search alone, share with those that know...
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Yoono
Comments
Its not entirely same as stumbleupon.
Both are social bookmarking tools but while stumbleupon primarily facilitates random browsing within interest-groups, Yoono comes with a RSS Reader, options to monitor and sharing browsing activity,and search & manage bookmark functions.