Consider using Clonezilla [1] instead. While dd will produce a sector-by-sector image of your medium (which can be terribly inefficient if you're using considerably less than 100% of its available space) Clonezilla is file system-aware for a number of common file systems and has built-in support for compression as well. It resembles the recently discontinued Norton Ghost this way but is fully FOSS.
I normally run it off a live CD/USB of Parted Magic [2], another tool I can wholeheartedly recommend.