I have noticed each time it rains, the driver and passenger sides floors always gets wet kind of. I have searched every where around the truck's windscreen, and seen nothing. Has anyone experienced this before, and what did you do to fix it?

 

Drain holes in the cowl area may be plugged up from dirt and leaves. Look under the grilled area below the windshield. There's a thread on this site somewhere detailing the process for cleaning it.

 

Also while it seems odd, 3rd brake light at the top back of cab often leaks and that water can end up at the front of passenger and drivers side of cab

And 3rd brake light is a very common leak point on Rangers, a known issue

Windshield leaks tend to be one side or the other, they rust out at bottom corner on one side, depends on how old the Ranger is