
I've been lurking in this community for a little while, and I'm really impressed with all the cool images that I've seen.
I realize that sometimes an impediment to getting into locations you'd like to photograph is lack of permission from the owners-- The building may be locked up or the chance of getting caught too great.
I recently worked as a location scout/manager for a feature film produced locally, and had the opportunity to explore (and photograph) lots of abanded places as potential shooting locations. It amazed me how much access I was granted for this purpose. The people who showed me around were often very knowledgable about the building's history, and sometimes would even show me their favorite architectural/decor oddities. A lot of times the owners were eager to show around someone who was interested and respectful of the property.
Just an idea for those of you who might be interested: You might be able to get access to some prime abandoned places if you work out a deal with your local/state film commision. One of the duties of a film commision is to lure productions by providing photos of interesting locales, and even pre-scouting places with a desired goal in mind. They might be very glad to get free photos of area landmarks and interesting buildings, and local property-owners might be very open to letting their property be photographed (by a photographer with some legitimacy from the commission) in the hopes of it being used in a film or TV production in the future.
While location photos generally aren't shot with artistic quality in mind, it's very possible that you could do both-- Documenting what the area is like for production consideration, and also doing some 'pretty' shots.
There are lots of factors besides aesthetic appeal to keep in mind when scouting, such as proximity of a working power source, ceiling height, acoustic characteristics, space for a crew to stage in, parking area nearby, structural safety, etc. Your local film commission may be able to educate you about what to note and look for when you go to a location, and may be able to recommend ways to improve your work for their purposes.
Just an idea that struck me. About four months ago I would have killed to have an army of you guys helping me out, searching for usable places in my city!