SyncFriend is an Outlook plugin that lets you back up your contact list online for safe-keeping. After registering for an account with the service, you can back up your contacts lists to the SyncFriend server while also keeping that list updated on your mobile phone, too.
The SyncFriend plugin creates a menu that appears at the top of your Outlook inbox, where you can access your account information as well as start and stop your syncs. If you prefer, you can choose to just sync a specific contact folder to the service, instead of the whole thing.
Other features of this service include mobile clients, address book de-duping and calendar sync between Outlook and your phone.
More Info: SyncFriend