Visible crew/equipment: In Mary Ann's kitchen, just as Ray comments, "Ok, well you hungry? I'll get you some food," the clear reflection of a male crewmember moving around is visible in the glass window behind Ray. Then just as he says, "This is ketchup and mustard," another older male crewmember is visible directly in front of Rachel's reflection. (00:35:45)
Visible crew/equipment: When Ray and Ogilvy play tug-of-war with the gun, as the aliens rummage around the cellar, Ogilvy finally pulls it away from Ray. In the next close-up of Ogilvy and his gun, the boom mic dips down for a moment, but it's gone in Ogilvy's next close-up. (01:28:15)
Visible crew/equipment: In the scene when Ray is fleeing Mary Ann's destroyed home in the van. Right before he says "Robbie, get in." You can see a cameraman in the reflection of the van, right before it stops.
Visible crew/equipment: After the ferry disaster, and close call with the car, the trio are underwater swimming up towards the surface. When Robbie turns his head to the side the regulator in his mouth is visible. (01:03:45)
Visible crew/equipment: When Robbie gets out of Tim's car there are two of the crew's chalk marks on the sidewalk - one long blue line in front of Ray and an orange arrow near the trunk of the car. They are gone when Rachel leaves the car. (00:05:00)
Visible crew/equipment: After the plane has crashed Ray walks out of the house and towards the aircraft engine, as he walks behind the engine and before he comes from behind the engine, look at the right and to the rear of the engine, you will see a crew member move out of shot.
Visible crew/equipment: During the ferry disaster, while Ray, Robbie and Rachel are in the water, when the car heads toward them a vertical cable is visible at the left side of the car, beside the side view mirror. (01:03:30)
Visible crew/equipment: When the first ship is beginning to emerge from the ground, we see a shot of two men on top of a swaying scissor lift, notice in the close-up there is nothing between them. When the shot cuts to a wide view, a camera covered by tarps appears between the two men.
Visible crew/equipment: When Tom Cruise comes back in off the street covered in ash, he slumps down by the refrigerator and very quickly the boom mic falls down into shot almost hitting Tom on the head.
Visible crew/equipment: As Ray drives and Rachel screams, the camera crew and equipment are reflected in the window.
Answer: They're reported to be about 100 feet tall.
Which is about 30.5 meters.
lionhead
They definitely seemed a lot taller than 100ft in the movies though that's for sure. I would have guessed maybe a few hundred feet.