Force fields can be used to add effect to many of Blender's physics systems (Such as wind to blow particles and cloth, turbulence to smoke, etc.)
There are thirteen different Force Fields, not including Gravity which is located in the Properties > Scene Panel.
The thirteen forces are:
All the physics systems are effected by force fields except for:
The Fluid dynamics system is effected by the scene Gravity, but not any of the other forces.
The Ocean Modifier has it's own settings for wind velocity, direction, etc.
The Collision modifier only causes other dynamic objects such as particles and cloth to collide with it, otherwise it remains completely static.
The Dynamic Paint system has no interaction with Force Fields
All the physics systems that do interact with Force Fields have a panel (Field Weights) for individually controlling force field influence for that system.
More details about each Force Field can be found on the wiki