This is not hardcore, so flame away. My wife has been driving our 2003 Silverado for a few weeks and tols me that the carpet gets wet on the driver's side, even whe nit is parked. I won't have a chance to look at it for a few days, but any idea where the leak may be coming from? Is this a common problem?

Check A/C drain and windshield seal. Do you use coolant?

windshield seal is probably best bet, i had the same problem with leaks on the driver side, put some rtv up top and it went away.

that or the heater core..

that or the heater core..

I would think that as an option if it were the pass. side but OP said D. side....

It was common on the earlier trucks and mostly on the pass. side. It was usually attributed to one of the cowl trim screws that entered into the pass compartment. I do not recall if the screw was one that held the far right cowl trim piece...the little tri-angle piece of trim (ohh, that sounds good.. ;) ) or a screw that held the A/C duct to the firewall? You may try looking at all the trim screws in the cowl area and possibly look up under the dash and see if you can see any trace water paths. The remedy was to remove the screw silicone it and replace the screw.

I will check those things. It has to be something like the windshield seal or cowl because it only does it when it rains. I first thought there was something on the floor leaking, but I noticed that it also gets wet when it is just sitting in the driveway and and it is raining.

Take it to any reputable windshield replacement shop. Let them know what the problem is, have them repair it. I just did one today that was leaking on the passenger side, I had to pull the windshield and grind the rust off the pinchweld so the urethane would adhere correctly.