Just to remind everyone, these places are private property and can be dangerous. Yesterday I was on an abandoned farm that had been torched and littered with abandoned cars/trucks/etc just shooting for class and for fun. After about an hour there I was switching out a roll of film and as I looked up I saw a man holding a .45 in his hand and asked me very directly what I was doing there. I managed to explain that I was just a photographer for class and I did not touch or damage anything, he said he had been watching me for the past 10 minutes and the fact that I didn't touch anything was the only reason I wasn't being shot at or being arrested. After talking to him for a good 10 minutes with the utmost respect (rule of thumb: say "Sir" to anyone holding a gun) he explained it was his fathers farm and he comes though once a week to board everything back up that the vagrants try to break open and steal/scrap. He said that because I was doing it for class that he was ok, "if they had stayed in school they wouldn't be ruining my family's old home".
After talking about the history of the place he said that because I had been so respectful and honest that it was ok for me to finish up taking my photos and get the hell out of there, just not to come back.
So be careful out there, be respectful of whats not yours, take images, not items, break nothing, you might not know if an owner is watching. Let alone watching with a gun. That being said, I got some great shots, expect them later.