Menu path autocomplete changes the input field for menu path to an autocomplete text field while you are adding a menu item.
While entering characters into this field you will get a list of all matching node titles (and - if path is enabled - all matching URL aliases). Selecting one item will insert the internal link to it.
Version 7.x is named "Multi path autocomplete" because it doesn't alter fields for menu paths only.
#D7CX: Easy pledge since there is a full Drupal 7 release already.
Development on Menu path autocomplete is sponsored by undpaul