damp carpet... any thoughts?

So alittle while back I lifted up the front drivers side floor mat, and noticed the carpet underneath was somewhat damp. There must be some type of leak somewhere or something strange is going on. It's an 03 Xterra, and I have lifted up the carpet abit but havent been able to see much, probably will have to do a more thorough job soon.
I was looking for any tips or if anyones ever had this or done this before? Could it have anything to do with the sunroof? I was told about a drainage area for the sunroof, but couldn't find what the dealer was talkin about. Any help would be appreciated.
Thanks, Shane.

I have noticed the same problem. But, on the passenger side. I just dropped it off at the dealer today. So I will let you know what I have found out. Although it is a different year. It may help, you never know.

My problem was. A/C drain was leaking on the passenger floor.

hhmmm. i see. i just dont want to spend a couple hundred bucks extra just so the dealer can figure out if they can even fix it. i'm trying to find a company that specializes in leaks. we'll see, havent done too much yet about it.

I've seen this in other vehicles and it's what immediately came to mind when I saw the first post.... it gets my vote.