Nimbuzz, a Netherlands based VoIP & Messaging start-up is introducing a premium calling service called NimbuzzOut. This premium calling service is available via an upgrade of their mobile client, which is currently available from the iPhone’s iTunes Apps Store, the Ovi store and Getjar. So far Nimbuzz has offered a meta-client that works on PC, Mac, Symbian, Android and the iPhone and allows you to sign-in into any IM service including Skype. NimbuzzOut is the first step towards revenues for the company that has taken in an undisclosed amount of funding from Mangrove Capital Partners, original backers of Skype. In addition to Skype, Truphone and Fring are two other competitors for this fast growing service. Nimbuzz has been adding about 40,000 users a day or about million new registrations every month and now has a total of over 10 million registered users. The company says nearly 30 percent of those registered are regular users.

Nimbuzz has certainly come a long way — almost three years ago. At the time of its launch, we were pretty critical of the VoIP-on-m