While exploring the vast maze of halls and stands that is 3GSM... sorry... I mean the Mobile World Congress, a colleague and I stumbled across this little gem: Zyb.
They started off as an address book and calendar back-up service. Using a phone that supports SyncML you can back up and restore to and from their servers. You can also choose to let other Zyb users who are in your address book link to your contact data so if you change something it shows up at their end automagically.
They are now expanding this into a hub for all your online, social networking activities. It can aggregate your activities from services like Facebook, Twitter, LinkedIn etc. and share them as a feed with your friends. The plan is to bring this functionality to your phone too in the form of a Java app.
It also ties in with online services like Google maps. They showed us a neat demo where you can plan a meal out with a friend. First you choose the friend from your address book. Then it shows a map of where that friend lives and find nearby restaurants. You choose the one you want and it notifies the friend and saves the address and phone number of the restaurant into your address book which can then be sync'd back to your phone. Pretty cool.