Par­al­lax is a very inter­est­ing plugin for jQuery that allows you to create a Par­al­lax effect:

Par­al­lax turns a selected ele­ment into a ‘window’, or view­port, and all its chil­dren into absolutely posi­tioned layers that can be seen through the view­port. These layers move in response to the mouse, and, depend­ing on their dimen­sions (and options for layer ini­tial­i­sa­tion), they move by dif­fer­ent amounts, in a par­al­laxy kind of way.

This is pretty neat stuff. I’m rack­ing my brain trying to think of gra­tu­itous ways to use this in my next design project. So far I’m only think­ing of run­ning dogs…