Skype has been striking deals with mobile phone makers. In fact they just announced a deal with Nokia to have Skype bundled on Nokia phones.
The first phone to see the new Skype will be the N97 Nokia's flagship Smartphone. Skype will be integrated heavily into the phone, including being part of the address book so that you will be able to see which of your contacts are online with Skype straight from there.
Skype and Nokia are also going to allow the service to work over both the 3G and Wifi networks. This would mean messaging and VoIP calls even when you are not at a hotspot.
There is some concern that Nokia phones sold in the US would have this stripped from them as Skype on a mobile is a large fear for US cellular providers.