Keyboard shortcut in Finder for selecting a different custom Favorite?
You could use an application like Alfred or Automator services to assign shortcuts for opening folders:



If you want to open the folders over the current Finder window, you could use FastScripts to assign shortcuts to scripts like this:

tell application "Finder"
    reopen -- open a new file browser window if there are no open ones
    activate -- make Finder frontmost if the script was run with a global shortcut
    tell window 1
        set target to POSIX file "/Library/"
    end tell
end tell


Default Folder X allows adding custom shortcuts that work in both file dialogs and Finder.