Here's another company looking to take on an established giant.

Vopium, a mobile VoIP provider, raised $16.5 million from Raghuvinder Kataria, one of the earliest investors in Bharti Tele-Ventures, now known as Bharti Airtel, one of the largest telecom companies in the world. Kataria now owns the majority of the shares in Vopium.

"We believe that the market demands an alternative mobile solution to Skype and the fast market penetration of smartphones opens up new and more intelligent ways of communication," said Kataria. "Vopium’s solution is unique because it offers the best conversation quality and is easy to use."

Vopium's focus right now is cheap and low-rate international mobile calls. The free mobile app, which works with over 900 different handsets (including HTC, Motorola, and Nokia), promises to deliver the very best quality phone call at rates much lower than those offered by traditional phone companies.

In addition to calling, Vopium comes packaged with support for Facebook, MSN, AIM, ICQ, and Twitter, so that users have no excuse for getting their social on. Calls to Skype, Google Talk, and other Vopium users are always free.

Of course, taking on Skype will be no easy task. At peak times, 23 million people are using the popular VoIP service. According to their own figures, Skype is responsible for 12% of global international calling minutes, with users making 3.1 billion minutes of calls to landlines and mobile phones in the Q3 2009. In Q4 2009, Skype users made 36.1 billion minutes of Skype-to-Skype calls, and over a third of these were video calls.