In Joomla 1.5 the trash could be accessed via Menus -> Menu Trash and Content -> Article Trash. In Joomla 2.5, this have been changed to be accessed via the filters.
The process for accessing the menu and article trash is the same. Once you have trashed an article or menu item, simply select "trashed" from the filter:
This will display all your trashed articles or menu items. You will now see the icon in the toolbar to empty your trash: