
Luis pointed me to the Keyboard prefernces pane and the Full Keyboard Access tab. Check the box that says "Turn on full keyboard access" and choose between control and function keys, letters, or custom-defined letters.
Once enabled, you can access the menu bar and dock solely with the keyboard. Use the arrow keys after activating the menu bar or dock to navigate, and use ENTER to select items. Use the up arrow in the dock to display and select the pop-up menus.
Full keyboard access works great in Cocoa and Carbon applications, but not at all in Classic (as you might expect).

