As requested by Jessie Hooper, here are some sites to find virtual dice to roll. Each of these have animation, which makes the experience a little nicer for the students. Jessie was using these to teach counting to her Pre-K students in centers, but the links can just as easily be used for teaching probability in later grades.
Virtual Dice – has a decent animation – not very dice like.
VirtualDiceRoll.com – a little more realistic with nice animation. Small on the screen so you will have to zoom in to project for the class.
TeacherLED.com dice roller – nice animation, easy to read. This is another good site.