EQO, based in Vancouver, BC has developed a way to take Skype with you on a cell phone. It's sorta neat, but what it really does is manage Skype forward/skype in/skype out.
The real play is how they can bring any online community to the handset, but on the Circuit Switched side, not the Data side. They use GPRS to grab pseudo-presence data (i.e. not always on, not real time) to map the call over to the voice side.
This is a nice first step, but BridgePort Networks has a more complete and real solution that works with IP, Mobile and VoIP and will interface with the leading IM players too, like MSN, AIM and YAHOO Messengers, all of which are now SIP based very elegantly and easily.