RIM offers this free app and service that automatically backs up the data on your BlackBerry as often as you feel you need (mine is set to once per week).   I don’t need to sync my BB that often so with this app I know that the changes I make on the fly to my address book and calendar will get backed up.  I highly recommend that you take advantage of this service.

Free BlackBerry Protect – Download BlackBerry Protect – Free Apps from BlackBerry App World.