I don't take much for granted, other than the usual - having all my limbs (including my penis), having food, having a roof above my head, breathing free air and drinking clean water, having plenty enough possessions, etc. But I'll go with something specifically no one has really mentioned - the Internet.
I heard once that back in the Dark Ages, one open piece of newspaper would contain more information than the average person would come across in their entire lives. Compare that to the mighty internet we have here in the 21st century. You have an almost endless access to other people's lives (message boards like this one) and countless media such as movies, videos, songs (feel like I should just say Youtube), endless information on several different subjects, and a whole host of other stuff that you would otherwise have no access to.
Before I had internet, I recall being in disbelief that such a marvelous thing could ever be invented and become common place in the average household. Then, in July 2003, I first got access to it and just couldn't get enough of it. Fast forward ten years later to June 2013 and the internet to me is just another materialistic possession in the house, no different than the bazillions of movies and video games lying around somewhere in this same room, most that I hardly ever watch or play anymore. I enjoy it and frequent it every day but I just don't grasp (and neither does probably 99.9% of other people) how shitty it would be if it disappeared altogether.