5. Palantir Technologies

Estimated Value: $3.5 Billion

Last Year's Rank: #11

Business:  Analytics software / platform

Location: Palo Alto, California

CEO: Alexander Karp

Palantir Tech is a data analytics platform focusing mainly on the government and financial sectors.

Palantir is estimated to generate between $350 and $400 million this year from its subscription product, up from $100 million in 2011.

#4 360Buy

Estimated Valuation: $5 billion

Last Year's Rank: #4

Business: E-commerce

Location: Beijing, China

CEO: Liu Qiangdong

It is a Chinese e-commerce company, and largest B2C (business to consumer) online retailer in china.

Described as the Amazon of China, it raised 1.5 billion and was valued at $6.4 billion at the beginning of 2011, led by Digital Sky Technologies. It generated $1.7 billion in sales in 2010 and $3.3 billion in 2011.

#3 Twitter, $5.25 billion

Estimated Value: $5.25 billion

Last Year's Rank: #5

Business: Messaging, microblogging and social networking service

Location: San Francisco, CA

CEO: Dick Costolo

Twitter has been growing very quickly both in terms of users and revenue. Its revenue for 2011 was $139.5 million and it's expected to generate about $350 million this year. Twitter has said it expects its revenue to jump to $1 billion in 2014.