Although their eyes don't actually move, jumping spiders can move their retina around inside their eye sockets in order to look in different directions. You know that they are looking at you when you can see the black of the retina.

This one appears a bit crosseyed, demonstrating their ability to move each eye independently.

The retinal movements probably benefit them by not requiring them to physically move in order to focus on their prey.

I suppose if you're already keeping up with eight eyes, a little extra eye movement for two of them won't bother you.

The Tree of Life Web Project has more information on jumping spider vision.