I'm using nice menu in my durpal-7 site.I need to show a subtitle for each menu item.How can this be done ? I'm new to drupal so it would be great if you could help me.
Try OM Maximenu module
"Maximize your main navigation by adding text, images, videos, slideshow, tabs, menu blocks, user info ..."
That is now possible by using OM Maximenu which can create menus with all other module blocks you want as attachments, modules like views, slideshow, menu, user, nice menus, quicktabs, and custom blocks with tables, lists, images, videos, etc.
Here a great list of menu 7 Mega Menu modules for Drupal