How to get camera plane ? 
game_maker  { Camera × Object } Collision
To do collision (Box or Shpere) I nead to got the plane from the view port => how can I get the Camera Plane ?

Eric Coleman  Assuming you know the camera's position, then you can easily find the camera's plane.
use the vector
v.x = ViewMatrix.m13
v.y = ViewMatrix.m23
v.z = ViewMatrix.m33
and then calculate
p.x = ViewMatrix.m11 + CameraLocation.x
p.y = ViewMatrix.m21 + CameraLocation.y
p.z = ViewMatrix.m31 + CameraLocation.z
And finally use the function D3DXPlaneFromPointNormal in the D3DX library were the vector v is your plane's normal and p is a point in the plane. 
game_maker  very nice ^^
but this gives me equation of plane  infnite plane ? what I need is finite plane [:)] 
VBBR  Wouldn't it be more easy just checking with a bounding box/sphere for the camera? 
Eric Coleman  The camera isn't in a finite plane, so I'm not sure what you're looking for. 
game_maker  To do collision I must first compute the camera boundary right?
I can't compute the boundary from equation of plane with no limit's right?
So I think what I need is to find the borders in camera's plane....
The view port is a rectangular rotated in xyz ... right?
See I am totally with you with math stuff:
Equation of Plane:
ax + by + cz + d = 0
We can find the equation (i.e. finding a,b,c,d) if we have the normal vector to the plane and any point in the plane as you said
N: is the normal vector to the plane <a1,a2,a3>
P: is general point in the plane <x,y,z>
P1 : is a known point in the plane <x1,y1,z1>
Ok if we find P1P vector = <xx1,yy1,zz1>
Notice that P1P is normal to N so the dot product is equal to zero
N . P1P = <a1,a2,a3> . <xx1,yy1,zz1> = 0
a1(xx1) + a2(yy1) + a3(zz1) = 0
a1x  a1x1 + a2y  a2y1 + a3z  a3z1 = 0
a1x + a2y + a3z ( a1x1 + a2y1 + a3z1) = 0
Finally:
a = a1
b = a2
c = a3
d = (a1x1 + a2y1 + a3z1)
Ok if we take camera's position + rotation it will be the center of our boundary.... I need one corner point [:)]
Am I doing this wrong ? [8)] 
Eric Coleman  Are you trying make the viewing frustum not collide with anything? I think you should probably do what VBBR suggests, use either a bounding box or sphere around the camera's position and test to see if that collides with anything. 