Figure-Ground Perception

We have a tendency to simplify a scene into a main object (figure) and then, everything else is used to form the background.
For example, you might see a maple leaf on this flag.. If you take another look you'll see two faces with pointy noses arguing. We simplify the flag to see a red leaf and therefore, the white is just a background for the image.

http://en.wikipedia.org/wiki/Figure%E2%80%93ground_%28perception%29
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Shape Constancy

Shape constancy is our ability to perceive an object as its original shape, even when it is positioned at different angles.

Even though these tables are tilted at different angles, we constantly perceive them to be the same original shapes.

opticalillusion.net

Brightness Constancy

Color remains the same no matter how it looks under different colors of light. If we didn't have this sense of color constancy, we would think that everything was always changing shades of color.

The image below shows the same flower shown in different brightness levels. Observe how the color appears to change. 

colorconstancy.com

Size Constancy

The perceptions of the size of objects is constant even though the size of the object on the retina varies with distance.
Everyone in the left photograph seems to be the same size right?

Take a look at the photograph on the right. The man in the white shirt was copied and pasted next to the woman on the left to show how the size varies with distance.

http://psych.hanover.edu/Krantz/sizeconstancy/page2.html

proximity

We tend to group nearby objects together. In this sweater, the holes are close together, so we group them together into lines that form shapes.

similarity

We group figures together that are similar. In this picture, we see columns of x's and columns of o's instead of rows of x's and o's because we group similar letters together.

X   O   X   O   X   O

X   O   X   O   X   O

X   O   X   O   X   O

continuity

We see smooth and continuous patterns instead of discontinuous parts. An example of this is a recycling symbol made of disconnected arrows because our minds see it as a complete circle.

Motion Perception

Humans are able to perceive motion.  We can tell if an object is coming or going, and not simply getting smaller or larger. For example, when we view a picture of someone walking, we can tell the direction  they are walking and the general speed at which they are walking.

Binocular Cues: Convergence

Binocular cues are involved in depth perception, and involve the use of both of our eyes.  One binocular cue is convergence, which is how much the eyes converge inwards when looking at an object.  The more inwardly the eyes are focused, the closer the object.  For example, when looking at a globe from a closer distance the eyes are more inwardly angled.  When looking at a globe from a farther distance, the eyes are not as sharply angled.

Monocular Cues: Texture Gradient

Texture gradient is the idea that an object's texture is more distinct when it is closer.  From farther away, the same object may appear smoother and more indistinct than it actually is.  For example: a brick wall.  From close up, you can really see all the crevices and rough edges of each brick, but from farther away it looks much more indistinct.

Monocular Cues: Linear Perspective

Linear perspective describes when two parallel lines appear to be converging, even though they are really not.  For example, when looking at a straight road, it appears to be getting narrower.

Closure

We fill in gaps to create a complete and whole object. In this panda picture, parts of the body are not connected, but our minds automatically connect the lines to see the complete shape of the panda.