1.

Look at Sid's backpack. On it is written "Julie Macbarfle has cooties!". Julie is the name of one of the head editors who said she wanted her name in the movie.

2.

The books on Andy's bookshelf are titled "Tin Toy" and "KnickKnack" among others. These were the names of some of the directors short films.

3.

Notice the "For Sale" sign in front of Andy's house. It says "Virtual Realty." Get it? (Virtual Realty, Virtual Reality)

4.

The tool box on top of the crate Woody's trapped in is labled "Benford Tools", the name of Tim Allen's tool company on "Home Improvement".

5.

When the baby in Andy's car looks out the window and sees the Slinky Dog, he giggles. You can also hear "Hakuna Matata" playing softly in the background. What gives?!