Rays of light through text in After Effects
 

How do I make that effect where a spotlight seems to shine from behind text as it moves from one side to the other (with rays of light piercing through the text)?

If you have After Effects 6.5 try the "Light Sweep" and "Light Burst" effects. Duplicate your text and apply the effect to the lower layer.

If you don't have After Effects 6.5 then I recommend taking a look at Trapcode Shine, http://www.trapcode.com/products_shine.html. From what I've heard it is a great plugin.

Trapcodes plug in is great. You can also try animating a light that you place behind the text.

Jim