Frustum::Frustum()
{
	getFrustum();
}

Frustum::~Frustum()
{
}

void Frustum::getFrustum()
{
   float   proj[16];
   float   modl[16];
   float   clip[16];
   float   t;

   /* Get the current PROJECTION matrix from OpenGL */
   glGetFloatv( GL_PROJECTION_MATRIX, proj );

   /* Get the current MODELVIEW matrix from OpenGL */
   glGetFloatv( GL_MODELVIEW_MATRIX, modl );

   /* Combine the two matrices (multiply projection by modelview) */
   clip[ 0] = modl[ 0] * proj[ 0] + modl[ 1] * proj[ 4] + modl[ 2] * proj[ 8] + modl[ 3] * proj[12];
   clip[ 1] = modl[ 0] * proj[ 1] + modl[ 1] * proj[ 5] + modl[ 2] * proj[ 9] + modl[ 3] * proj[13];
   clip[ 2] = modl[ 0] * proj[ 2] + modl[ 1] * proj[ 6] + modl[ 2] * proj[10] + modl[ 3] * proj[14];
   clip[ 3] = modl[ 0] * proj[ 3] + modl[ 1] * proj[ 7] + modl[ 2] * proj[11] + modl[ 3] * proj[15];

   clip[ 4] = modl[ 4] * proj[ 0] + modl[ 5] * proj[ 4] + modl[ 6] * proj[ 8] + modl[ 7] * proj[12];
   clip[ 5] = modl[ 4] * proj[ 1] + modl[ 5] * proj[ 5] + modl[ 6] * proj[ 9] + modl[ 7] * proj[13];
   clip[ 6] = modl[ 4] * proj[ 2] + modl[ 5] * proj[ 6] + modl[ 6] * proj[10] + modl[ 7] * proj[14];
   clip[ 7] = modl[ 4] * proj[ 3] + modl[ 5] * proj[ 7] + modl[ 6] * proj[11] + modl[ 7] * proj[15];

   clip[ 8] = modl[ 8] * proj[ 0] + modl[ 9] * proj[ 4] + modl[10] * proj[ 8] + modl[11] * proj[12];
   clip[ 9] = modl[ 8] * proj[ 1] + modl[ 9] * proj[ 5] + modl[10] * proj[ 9] + modl[11] * proj[13];
   clip[10] = modl[ 8] * proj[ 2] + modl[ 9] * proj[ 6] + modl[10] * proj[10] + modl[11] * proj[14];
   clip[11] = modl[ 8] * proj[ 3] + modl[ 9] * proj[ 7] + modl[10] * proj[11] + modl[11] * proj[15];

   clip[12] = modl[12] * proj[ 0] + modl[13] * proj[ 4] + modl[14] * proj[ 8] + modl[15] * proj[12];
   clip[13] = modl[12] * proj[ 1] + modl[13] * proj[ 5] + modl[14] * proj[ 9] + modl[15] * proj[13];
   clip[14] = modl[12] * proj[ 2] + modl[13] * proj[ 6] + modl[14] * proj[10] + modl[15] * proj[14];
   clip[15] = modl[12] * proj[ 3] + modl[13] * proj[ 7] + modl[14] * proj[11] + modl[15] * proj[15];

   /* Extract the numbers for the RIGHT plane */
   frustum[0][0] = clip[ 3] - clip[ 0];
   frustum[0][1] = clip[ 7] - clip[ 4];
   frustum[0][2] = clip[11] - clip[ 8];
   frustum[0][3] = clip[15] - clip[12];

   /* Normalize the result */
   t = sqrt( frustum[0][0] * frustum[0][0] + frustum[0][1] * frustum[0][1] + frustum[0][2] * frustum[0][2] );
   frustum[0][0] /= t;
   frustum[0][1] /= t;
   frustum[0][2] /= t;
   frustum[0][3] /= t;

   /* Extract the numbers for the LEFT plane */
   frustum[1][0] = clip[ 3] + clip[ 0];
   frustum[1][1] = clip[ 7] + clip[ 4];
   frustum[1][2] = clip[11] + clip[ 8];
   frustum[1][3] = clip[15] + clip[12];

   /* Normalize the result */
   t = sqrt( frustum[1][0] * frustum[1][0] + frustum[1][1] * frustum[1][1] + frustum[1][2] * frustum[1][2] );
   frustum[1][0] /= t;
   frustum[1][1] /= t;
   frustum[1][2] /= t;
   frustum[1][3] /= t;

   /* Extract the BOTTOM plane */
   frustum[2][0] = clip[ 3] + clip[ 1];
   frustum[2][1] = clip[ 7] + clip[ 5];
   frustum[2][2] = clip[11] + clip[ 9];
   frustum[2][3] = clip[15] + clip[13];

   /* Normalize the result */
   t = sqrt( frustum[2][0] * frustum[2][0] + frustum[2][1] * frustum[2][1] + frustum[2][2] * frustum[2][2] );
   frustum[2][0] /= t;
   frustum[2][1] /= t;
   frustum[2][2] /= t;
   frustum[2][3] /= t;

   /* Extract the TOP plane */
   frustum[3][0] = clip[ 3] - clip[ 1];
   frustum[3][1] = clip[ 7] - clip[ 5];
   frustum[3][2] = clip[11] - clip[ 9];
   frustum[3][3] = clip[15] - clip[13];

   /* Normalize the result */
   t = sqrt( frustum[3][0] * frustum[3][0] + frustum[3][1] * frustum[3][1] + frustum[3][2] * frustum[3][2] );
   frustum[3][0] /= t;
   frustum[3][1] /= t;
   frustum[3][2] /= t;
   frustum[3][3] /= t;

   /* Extract the FAR plane */
   frustum[4][0] = clip[ 3] - clip[ 2];
   frustum[4][1] = clip[ 7] - clip[ 6];
   frustum[4][2] = clip[11] - clip[10];
   frustum[4][3] = clip[15] - clip[14];

   /* Normalize the result */
   t = sqrt( frustum[4][0] * frustum[4][0] + frustum[4][1] * frustum[4][1] + frustum[4][2] * frustum[4][2] );
   frustum[4][0] /= t;
   frustum[4][1] /= t;
   frustum[4][2] /= t;
   frustum[4][3] /= t;

   /* Extract the NEAR plane */
   frustum[5][0] = clip[ 3] + clip[ 2];
   frustum[5][1] = clip[ 7] + clip[ 6];
   frustum[5][2] = clip[11] + clip[10];
   frustum[5][3] = clip[15] + clip[14];

   /* Normalize the result */
   t = sqrt( frustum[5][0] * frustum[5][0] + frustum[5][1] * frustum[5][1] + frustum[5][2] * frustum[5][2] );
   frustum[5][0] /= t;
   frustum[5][1] /= t;
   frustum[5][2] /= t;
   frustum[5][3] /= t;
}

int Frustum::sphereInFrustum(float x, float y, float z, float radius )
{
	ofstream logger("frustumLog.txt", ios::app);
	logger << "Checking sphere at (" << x << ", " << y << ", " << z << ") with radius: " << radius << endl;;
	int p;
   float d;
   int planesCleared=0;

   for( p = 0; p < 6; p++ )
   {
      d = frustum[p][0] * x + frustum[p][1] * y + frustum[p][2] * z + 
		  frustum[p][3];
      if( d <= -radius )
	  {
		logger << "Failed on plane " << p << " @ distance " << d << endl;
		logger.close();
		  return 0;
	  }
	  if (d>=radius)
	  {
		  planesCleared++;
	  }
   }
   if(planesCleared==6)
   {
	   logger << "Cleared all planes!" << endl;
	   logger.close();
	   return 2;
   }
   else
   {
	   logger.close();
	   return 1;
   }
   
}


The box class:
   
void Box::calcBounding()
{
	if(length >= height && length >= width)
		boundingRadius=length;
	else if(height >= length && height >= width)
		boundingRadius=height;
	else
		boundingRadius=width;

}


The linked list of scene objects (ie drawing code):
   
void ObjectList::drawObjects(Camera *cam)
{
	Object* current=head;
	int x =0;
	glInitNames();
	glPushName(0);
	while(current !=NULL)
	{
		// Draw the bounding sphere

			glLoadIdentity();
			cam->draw();
			glColor4f(1.0f,1.0f,0.0f,0.8f);	// Full Brightness, 50% Alpha ( NEW )

			glEnable(GL_BLEND);			// Turn Blending On

			glDisable(GL_DEPTH_TEST);
			glTranslatef(current->getX(), current->getY(), current->getZ());
			auxSolidSphere(current->getBoundingRadius());
			glDisable(GL_BLEND);			// Turn Blending On

			glEnable(GL_DEPTH_TEST);
			glColor4f(1.0f,1.0f,1.0f,1.0f);
		// End bounding sphere


		if(cam->viewFrust.sphereInFrustum(current->getX(), current->getY(), current->getZ(), 
			current->getBoundingRadius()) !=0 )
		{
			x++;
			glLoadIdentity();
			glPushMatrix();
			(*cam).draw();		// Set the viewpoint

			glLoadName(x);
		
			(*current).draw();	// Draw the object

			glPopMatrix();
		}
		current=(*current).getNext();	// Move to the next object

	}
}


And last but not least, the actual engine code:
   
//init         

Box *boxer=new Box(2.0f, 2.0f, 2.0f);
boxer->setColors(0.0f, 1.0f, 0.0f);
	lister.setHead(boxer);
	Box *boxest = new Box(0.5f, 0.5f, 0.5f);
	boxest->setColors(1.0f, 0.0f, 1.0f);
         boxest->move(-3.0f, 3.0f, 1.0f);
	lister.addItem(boxest);


And the output that I get when running the program and constantly moving around:
   
Checking sphere at (0, 0, 0) with radius: 2
Checking sphere at (-3, 3, 1) with radius: 0.5
Checking sphere at (0, 0, 0) with radius: 2
Checking sphere at (-3, 3, 1) with radius: 0.5
Failed on plane 1 @ distance -2.62611
Checking sphere at (0, 0, 0) with radius: 2
Checking sphere at (-3, 3, 1) with radius: 0.5
Failed on plane 1 @ distance -2.62611
Checking sphere at (0, 0, 0) with radius: 2
Checking sphere at (-3, 3, 1) with radius: 0.5
Failed on plane 1 @ distance -2.62611
Checking sphere at (0, 0, 0) with radius: 2
Checking sphere at (-3, 3, 1) with radius: 0.5
Failed on plane 1 @ distance -2.62611
//Repeat pattern of last three lines until EOF