The GSMA Mobile World Congress appears to be the best moment for announcing new partnerships and collaborations. Skype’s presence at the event appears to be connected to its plans with Nokia, as the two companies announced earlier today that they managed to reach an agreement.

Nokia, which is the world’s biggest cell phone maker, will begin selling its handsets with Skype’s software installed. At first, the new feature will be available on the company’s high-end devices, the N-series. The N97, which is scheduled for release in June, will be the first to use Skype’s service.

The new feature will be integrated into the phone’s address book, allowing users to view their online contacts and also letting them use Skype’s instant-messaging client. The companies announced that Skype-to-Skype voice calls will be free and also, the SkypeOut service, which allows calls from Skype to landlines and mobile devices, will provide very low rates. Another significant plus is the fact that N97 users will be given the possibility to make free and low-cost phone calls over the Internet whether they will be on a 3G cellular network or a Wi-Fi network.

“Making Skype available everywhere through mobile devices is essential to fulfilling our vision of ‘enabling the world’s conversations’,” explained Scott Durchslag, Skype’s Chief Operating Officer, who also added that the preloaded software, which will be easily accessible and simple to use, will greatly benefit many Nokia customers.

Skype’s services are not exclusive, as Sony also announced yesterday that its Windows Mobile Xperia 1 device will offer a Skype panel.