Adobe apps have a Help system, but there's also web versions called LiveDocs that give you Help as well as a list of resources and new features. To find them just go to the Help Resource Center, pick an app, then click on LiveDocs. The advantage of these is they are continually refined and updated by Adobe. Also, when you're at a LiveDocs site, like the one for AE8, you can easily Go to the Photoshop LiveDoc via the pulldown menu in the left pane.
Incidentally, you can suggest revisions or just add information on any of the topics by posting comments directly onto the LiveDocs pages.