Many Flannery O' Connor stories deal with this idea. In "The Life You Save May Be Your Own", a mother and a drifter have different perceptions of the woman's daughter, & the reality is something completely separate from what they both think. In "Good Country People", a young woman's perception of her life and philosophy are challenged by a traveling Bible salesman.
I agree with poster #1 with regards to Ray Bradbury. Any of the stories from The Martian Chronicles would serve well, as they deal with the perceptions of aliens and what it means to be human. Also, stories such as "The Highway" and "The Other Foot" deal with humanity's perception of our place in time and space. Amazing.
Finally, J. D. Salinger's Nine Storieshas some incredible moments of questioning our perception of ourselves, and the ways in which we interpret our consciousness.