There are a few places where it would be useful if plugins could add in their own menu items, to give useable navigation.

Although I am sure there are other areas where menu item plugability would be useful, the following are areas that we have come up against (in importance order):

1. Space Administration - being able to add items to a category ("Space Operations" for example) or even creating a new category.
2. Space Actions Tabs - being able to add a tab to to the list or a sub tab (eg: a new page view along side Tree View / A-Z)
3. Administration Menu - same as Space Administration.

Each item would contain a title, icon and URL (which should expand common variables like $spaceKey).