I'm fascinated with old buildings as well. Some years ago I worked at a bar in town that was attached to an old turn of the century hotel that had fallen into a state of disarray. It was beautiful in its heyday, I'm sure. Anyway, we would grab a flashlight and take people on tours (usually drunk people)...all the way up to the tiny servants quarters, looking over the ballroom, into the basement that supposedly connected every building on the block.
Finally, my town did something right and renovated it for public use. It's beautiful.
I find old abandoned things (whether they be amusement parks, hotels, factories) amazing (have visited the opacity site linked here): there's a "feeling" about them, a history.
I didn't see this site posted, but I'm looking hurriedly from work, so I apologize if it's been posted, but I like this site: (edit: it won't let me link since I'm such a newbie...google The Willard Suitcase Exhibit. Sorry)