Camera.OnPostRender  

// This script lets you enable/disable fog per camera.
// by enabling or disabling the script in the title of the inspector
// you can turn fog on or off per camera.

private var revertFogState = false;

function OnPreRender () {
    revertFogState = RenderSettings.fog;
    RenderSettings.fog = enabled;
}

function OnPostRender () {
    RenderSettings.fog = revertFogState;
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    private bool revertFogState = false;
    void OnPreRender() {
        revertFogState = RenderSettings.fog;
        RenderSettings.fog = enabled;
    }
    void OnPostRender() {
        RenderSettings.fog = revertFogState;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    private revertFogState as bool = false

    def OnPreRender():
        revertFogState = RenderSettings.fog
        RenderSettings.fog = enabled

    def OnPostRender():
        RenderSettings.fog = revertFogState