You can calculate escape velocities by using the conservation of energy. In other words, we need to realize that the kinetic energy needed to escape has to be equal to the gravitational potential energy.

Given that
Gravitational P.E. = -----

Kinetic Energy = -----

       / 2GM
v =   / -----
    \/    r

Where G is the universal gravitational constant (6.67 * 10-11 m3 / kg * s2), M is the mass of the body and r is that body's radius. The escape velocity for different planets in the solar system are approximately:

Mercury: 4.25 km/s
Venus: 10.36 km/s
Earth: 11.18 km/s
Mars: 5.02 km/s
Jupiter: 59.64 km/s
Saturn: 35.41 km/s
Uranus: 21.41 km/s
Neptune: 23.52 km/s
Pluto: 1.00 km/s