Yahoo has an interesting application for mobile phones called Yahoo! Go. Install Yahoo Go on your mobile phone and it will sync your contacts between your phone and Yahoo Mail. Whether you’re adding contacts online or on your phone, you can use Yahoo Go to sync them. Of course there are many other features, but the address book sync is what makes it worth it.
Install Yahoo Go on your Blackberry device, and now your mail and contacts are backed up and synced online (providing you setup your Yahoo Mail account on your device). It’s simply a great solution, I only wish I could sync my calendar with Yahoo as well.