Shader for blending skyboxes in Unity3D via http://forum.unity3d.com/threads/213679-4in1-blending-skybox-HELP!

SkyboxBlended.shader

Shader "RenderFX/Skybox Blended" {

Properties {
    _Tint ("Tint Color", Color) = (.5, .5, .5, .5)
    _Blend ("Blend", Range(0.0,1.0)) = 0.5
    _Skybox1 ("Skybox one", Cube) = ""
    _Skybox2 ("Skybox two", Cube) = ""
}

SubShader {
    Tags { "Queue" = "Background" }
    Cull Off
    Fog { Mode Off }
    Lighting Off        
    Color [_Tint]
    Pass {
        SetTexture [_Skybox1] { combine texture }
        SetTexture [_Skybox2] { constantColor (0,0,0,[_Blend]) combine texture lerp(constant) previous }
        SetTexture [_Skybox2] { combine previous +- primary, previous * primary }
    }
}

Fallback "RenderFX/Skybox", 1
}