Digg, Inc., the leading social news site, raises $28.7 million series C investment round led by Highland Capital Partners also includes previous Digg investors Greylock Partners, Omidyar Network and SVB Capital, the expansion comes at a time when traffic to the site has doubled in the last year to more than 30 million monthly unique visitors.

Digg is planning for significant corporate expansion program, including the doubling of the company’s staff from 75 to over 150 by December 2009, a move to a larger corporate headquarters in San Francisco in early 2009 and expand Digg into other languages.

“This round of funding allows us to accelerate that momentum and build the team to deliver features that will continue to change the way people consume content on the web.” said Jay Adelson, CEO of Digg.

With approximately 30 million unique visitors a month, Digg is the leading destination for people to discover and share the best content from anywhere on the web. From the largest online destinations to the most obscure blog, Digg surfaces the best content as voted on by the community.

Highland Capital Partners has been the lead investor in such online media and Internet companies as Ask.com, Lycos, MapQuest, Quigo and VistaPrint.