Here are three videos on how to tie knots, including the square knot, sheet bend, two half hitches, clove, hitch, taut line hitch, and bowline. This includes all of the knots required to receive the First Class rank in the Boy Scouts of America. Videos are by Zac Goodwin.
How to Tie the Square Knot and Sheet Bend
How to Tie the Two Half Hitches, Clove Hitch, and Timber Hitch
How to Tie the Taut Line Hitch and Bowline