I had to put my heater on in my 2001 Dodge Ram on a hot day (85 degrees), I noticed water dripping from the front firewall. I opened the hood and noticed a small tube (1/2" in dia.) protruding from the firewall that the water was dripping from. It was just water, no antifreeze. Is this normal? Just an overflow of some sort?

That's the condensation drain. It is supposed to drip. If that tube became clogged the condensation from the evaporator would back up inside the vehicle.