Some really great and short examples of illusions. If you want an explanation of them, I have added a link to the corresponding Wikipedia article.
Checker shadow illusion
Checker shadow illusion: The pieces A and B are of the same color.
Ebbinghaus illusion
Ebbinghaus illusion: the first central circle seems to be smaller than the second central circle although they are of identical size.
The Müller-Lyer illusion is simmilar.
Fraser spiral illusion
Although you think you see a spiral, there are only concentric circles. This illusion is known as Fraser spiral illusion.
Grid illusion
Dark dots seem to appear and disappear in the Grid illusion.
Jastow illusion
In Jastow illusion, the two figures are identical, although the lower one appears to be larger.
Zöllner illusion
In the figure of Zöllner illusion the black lines seem to be unparallel, but in reality they are parallel.
Hering illusion
Hering illusion: Two straight and parallel lines look as if they were bowed outwards.
Spinning Dancer
This image is the only animated one in this post.
Spinning Dancer: If the foot touching the ground is perceived to be the left foot, the dancer appears to be spinning clockwise (if seen from above); if it is taken to be the right foot, then she appears to be spinning counterclockwise.
Illusory motion
Illusory motion: This image is not animated!
Café wall illusion
Café wall illusion: the parallel straight dividing lines between staggered rows with alternating black and white "bricks" appear to be sloped