Two things I remember most are big pipes (12 foot tall "rainbirds") used to cover the pad with water just before lift off, and the flame trenches.
Looking down into the flame trenches you could see where a few firebricks were missing, and in the distance there were holes in the chain link fence where they'd gone through.
Most people think that dumping water on the pad is so that things don't burn up, but it's actually for sound suppression. Here's more than you want to know about flame trenches and such:
The flame trench is 13 meters (42 ft) deep, 137 meters (450ft) long and 18 meters (58 ft) wide. The orbiter flame deflector is 11.6 meters (38ft) high, 22 meters (72 ft) long and 17.5 meters (57.6 ft) wide. It weights 590,000 kg (1.3 million lbs). The SRB deflector is 12.95 meters (42.5 ft) high, 12.8 meters (42 ft) long and 17.4 meters (57 ft) wide. It weights 499,000 kg (1.1 million lbs). The Sound Suppression Water System is used to protect the launch structure from the intense sound pressure of liftoff. Its water tank is 88.9 meters (290ft) high and has a capacity of 1,135,000 liters (300,000 gallons).The recent shuttle launch caused much more damage than usual. You can read about it here, but the pictures are great (scroll all the way down to see the bricks and fence), proof that I wasn't making up the story :)