Here are list of few modules which are very useful in drupal application :
The Admin Menu module let’s you navigate through the menu options somewhat faster than Admin module in my experience. I often will enable one of these for admins and use the toolbar for other logins
Drush is the standard for developer command line site administration. Drush stands for Drupal Shell
This module allows you to add email address as fields in Drupal 7 which is a pretty common use case.
In Drupal 7 you need this module to group fields together on a content type. This is helpful for editors as it provides visual clarity as to how fields should be grouped together on a page.
Allows you to add ‘link’ fields to content and has Views integration.
A must-have module. This is the reason why you are using Drupal. Views 3 is even more awesome than 2.0. I really like the updated workflow.
A must have SEO-based module for every site.
An SEO module for providing site maps to search engines.
Entities are a new Drupal 7 concept, this module is required by a lot of other modules because it exposes an API to entities, so chances are you are going to need this module installed
Pagerer is a module providing a collection of pager themes to enhance Drupal and Views standard pagers.
Administrators or site builders can preset multiple pager configurations. Each ‘preset’ allows a pager to be made up of three ‘panes’: left, center, and right. Each pane can contain (or not) a pager theme. In this way there is plenty of possibilities to combine different elements to satisfy complex requirements.
Note : There are a lot of modules but you can install based on your need such as commerce, blog, forum etc