Why do most planets rotate in a counter-clockwise direction (as viewed from above Earth's North pole)?

When a solar system is formed there's a certain amount of angular momentum in the system, which is a conserved quantity. So the planet's rotation is usually the same as the host star because of the conservation of angular momentum (you can think of this in terms of rotating spinning tops that conserve the "rotation amount" when colliding). The fact that most of the planets rotate in a counter-clockwise fashion is only true for our solar system, and it's not true for other stars in general. It all depends on the angular momentum the solar system began with during the collapse of the nebula.

This is actually a much more subtle question than the Wikipedia answer  of "the solar disk was rotating counterclockwise therefore planets  rotate counterclockwise". The rotation of the initial disk is enough to  explain why the earth is going counterclockwise <b>around the  sun<\b>, but its axial rotation implies that the material that  accreted to form Earth had (just a little) more angular momentum than  the Earth's current center of mass. This is actually counterintuitive:  if you imagine two rocks on nearby circular orbits, then the one closer  to the sun will be going faster (by Newton's laws), so if they scratch  against each other or combine into one bigger rock, they'll each start  rotating around their axes the wrong way, clockwise (think about it).  However this would also make the orbits a little more oblong. On  the other hand, when an object going counterclockwise around the sun  with an oblong orbit slows down to make the orbit more circular, its  center of mass must lose some angular momentum, and so collisions that  make this happen tend to impart some counterclockwise axial rotation. So  if I had to make a guess, I'd say the counterclockwise rotation of the  planets has to do with the regularity of their orbits: a bunch of rocks  with different irregular orbits combined to make a big rock with an  orbit that's much more regular (nearly circular). This would fit in with  the fact that comets and asteroids don't have a preferred axial rotation direction.

The solar nebula was irregular in shape. Upon being triggered by either a supernova explosion nearby or a huge star passing by the irregular shape made the nebula rotate in an anticlockwise direction. As the local regions of the nebula contracted to our sun and the planets the anticlockwise rotation only got faster due to conservation of angular momentum. Thus it was the initial anticlockwise rotation of the solar nebula that caused anticlockwise rotation of all planets. Venus, Uranus and Neptune's moon triton are exceptions which can be attributed to heavy impacts in the early stages of the solar system.

This link explains it : http://www.sjsu.edu/faculty/watkins/solarspin.htm You may not be able to view the diagrams, but that's not essential. Also there are some minor "typo" errors, but nothing too serious. The point is that the initial rotation of the cloud of dust and gas that eventually formed the planets could have been in either direction. So the Solar System is just the outcome of chance events.