Wow, there's lots of easter eggs hidden in this one. This site is a semi-spoiler though, so I only recommend looking at it if you've already seen the movie, or don't really care about spoilers (you've been warned):
One thing I will say though, is if you like Studio Ghibli (Princess Mononoke, Castle in the Sky, Howl's Moving Castle), you may recognize something there from Hayao Miyazaki. I won't say what it is, but you may be surprised.
http://www.slashfilm.com/2010/06/18/toy-story-3-easter-eggs/