Although it is on the expensive end of the backup software scale, Synchronize Pro X is extremely versatile and has saved my bacon through a series of drive failures (that resulted in Apple replacing my PowerBook). I currently have it running 4 different scheduled backups on my system and have another backup set up that activates when I attach a certain thumb drive: it syncs a selected group of folders to the thumb drive and then unmounts the drive automatically. Plug, sync, unplug--very cool.