Where is the History pallet in Photoshop CS4?

You can find it under Window --> History. It looks like this in the toolbar.

yupp..Window-History. but I just wanted to add that you are able to save a workspace if you like to use certain tools that Photoshop doesn't show in its default setting. a lot of tools in photoshop can be accessed many different ways, but I usually change my workspace depending on what Im working on just to make it easy to access brushes, layers, adjustments..the list goes on. Just work on setting up a custom workspace. Photoshop already does this in a way, giving you options between painting, proofing, typography, and web, but Ive found the most efficient way to access tools quickly is to just create a workspace that you know really well..