The horizontal lines on this optical give the impression that they are parallel to the horizon, such that you feel you could quite easily write between the lines normally. But that is not the case they actually rise from the left to the right at such an angle that the left hand side of the line is in the same place as the right hand side of the line below.

In this variation of the pencil optical illusion above we seem to have more pencils on the right than we do on the left!

Which spear on the left is connected to the one on the right? Click on the optical to reveal.

Just stare at the red cross.

Just imagine getting in the elevator in this skyscraper and going up to the ground floor!

This great animated gif uses white lines to split the images into 3 panels. This helps the elements of the animated images to “pop” out of the frame in front of the white lines and toward the viewer. The trick works because the white lines establish a clear reference point for the foreground. This gif also uses the text below to add to the 3D effect.
Credit tumblebuggie

The McGurk effect is a compelling demonstration of how we all use visual speech information. The effect shows that we can't help but integrate visual speech into what we 'hear'.

Stare at the picture on the left for one minute then look into the white space on the right to see the ghost.

I think this optical comes under the categorie 'things that make you look twice'. It was produced from the strange mind of JC Debroize. Check out his work here.

Can find all the eyeballs hiding in the marbles?

Here is another take on our Eye Color Illusion, but this time using the Statue of Liberty. By staring at the left image for a while the right image starts showing the statue in it's usual verdigris color. If you concentrate hard enough you can keep the green color there all the time.

You might think that these types of illusions always end up with the answer - 'They are both the same'. Well not this one. You might need to get your ruler out!

Ah, the Magic Eye. For years, it made dolphins and sharks extrude from the bedroom posters of ’90s teenagers, and now it’s bringing an entire music video to life. For their latest track, “Black Is Good,” indie band Young Rival — as well as director Jared Raab and programmer Tomasz Dysinki — decided to use random dot autostereograms to convey the images, creating an illusion of depth. If you can “decouple” your eyes correctly, that is.
To see this video, watch in 1080p HD and follow the instructions at the beginning. If you're having trouble try the crossed-eye version here : http://www.youtube.com/watch?v=uUO5al... 

Here is our latest illusion featuring BBC Click's beautiful presenter Kate Russell. Just click on the picture to see her the right way up. Sorry Kate.