dd can take a command line argument to show progress, but often you don't know you want to see the progress until after you have already started it (and are wondering why it is taking so long).  Run this in another terminal window and your dd will barf up it's progress every 600 seconds.

  dick=$(ps a | grep "dd if" | grep -v -E "(sudo|grep)" | sed 's/^ *//' | cut -d " " -f 1); while sudo kill -USR1 ${dick} ; do sleep 600 ; done