Marcus Downing

Adds an “Identifier” column to the All Posts and All Pages admin panels, and to any custom post types. 
This column goes just after the Title column and shows each page’s slug, indented if necessary.

Page Identifier Column

Adds an "Identifier" column showing a post of page's slug, just after the Title column.

robfelty

Category reminder uses javascript to assert that a category has been assigned 
to a post before publishing it. If no category is assigned, then it will 
prompt the user to assign before publishing.

Category Reminder

This plugin requires users to assign a category to each post other than "Uncategorized".

Page Identifier Column vs Category Reminder