To help teach my first year engineering physics students last term about forces, I used an example of someone climbing up a crevice with their feet on one side and their back on the other.  This pair of physics teachers also feels that rock climbing, by example, is a great way of explaining forces.  Though cheesy, this video may help to understand forces, and rock climbing: [youtube http://www.youtube.com/watch?v=VSHxa9WI7Qw?wmode=transparent]