What is currently in the LEGO Store Pick A Brick Wall?
The bricks in the Pick A Brick Wall are subject to change. As soon as the supply of one type of brick is exhausted in a store, they replace it with another type of brick. There is no particular rotation or order, it is just whatever happens to be in the delivery that the store gets from Lego.

From Lego.com:


  Selection varies by store and the elements are always changing


The brickbuildr.com website has a section dedicated to an effort to inventory each Pick A Brick Wall through submissions from the community (not the Lego store itself), but it is often a little out of date.