Clogged drains are a possibility but its also just as likely that the wetness is coming from water leaking past the plastic vapor barrier in the door. Quick way to check for this: feel for wetness along the bottom edge of the door panel, especially under the area where the door speaker is. If that's wet, then the water seeping past the inner vapor barrier and into the floor carpeting.
Check out the photos in the follow post:
http://986forum.com/forums/general-discussions/22781-drivers-side-footwell-wet.html