#16 Craigslist

Estimated Value: $2 billion

Last Year's Rank: #10

Business: Classified ads

Location: San Francisco, California

CEO: Jim Buckmaster

It is a classified advertisements website with sections devoted to jobs, real estate, items wanted, community, gigs and much more. It currently operates in 50 countries around the globe. The company charges only a small nominal percentage of its ads like real estate and jobs. With its credibility, if it charges lot more of its classifieds, it could generate a billion dollar more in revenue.

The estimated valuation as of last year is $2 billion.

#15 Spotify

Estimated Value: $2 billion

Last Year's Rank: #15

Business: Spotify is a digital music service that provides access to millions of songs.

Location: Stockholm, Sweden

CEO: Daniel Ek

It is a Swedish music streaming service offering digitally restricted streaming of selected music ranging from independent and major record labels like Sony, Universal.

Last year Spotify raised $50 million at a $1.1 billion valuation. This year it's expected to generate $889 million, up 160 percent from 2011.