I cry for anything related to sad animals too. I also volunteer about 40 hours a week with an animal rescue group, which means every day I get desperate e-mails from shelters with photos of the cats they have there that are going to be put down, begging me to find a place for them before they die. I can't find places for them all, so I'm sure you can imagine how much I cry. It can be pretty unbearable.
The Giving Tree always makes me cry, as does Charlotte's Web. There were many episodes of the show Lost this past season that sent me into crying fits, and even more episodes of Friday Night Lights (I bawled at the end of the season one finale).
Taylor, looking at lonely people can make me cry as well. My boyfriend told me about a guy he worked with who has one season ticket to see the Washington Capitals, because he is a widower. I cried for days over him, imagining how he loved his wife and then she died, and now he goes solo to hockey games. Later my boyfriend told me he had been mistaken, and the guy just likes to go to games alone--his wife is alive and well! I was about to kill my boyfriend when I found out. Along those lines, I cried hysterically during the flashback scene at the beginning of the movie Up.
I also cry sometimes when I see immigrants standing in groups, waiting for someone to pick them up for day labor. When it is the middle of the day and they are still waiting, I get so sad. It all seems so tragic sometimes.