OS X equivalent of Windows keyboard commands to access in-application menus?
You can use Ctrl + F2, which moves the focus to the  symbol in the menu bar. Then use the arrow keys to move around, or just type the start of a menu name to highlight it. With a menu name highlighted, hit Space to expand it. In an open menu, you can type the start of a menu item to highlight it. Once highlighted, press Space again to “click” it.

So, to get to “Save for Web &amp; Devices” in Photoshop, you could press Ctrl + F2, F, Space, Enter, S, ↓ until you focus “Save for Web &amp; Devices”, then Space.

Of course, the built-in keyboard shortcut for that option is much easier to type: ⌥ + ⇧ + ⌘ + S.