You can find all resources about Drupal here...
Here are some modules you should have in your every project:
- Authcache - Drupal 6, Drupal 7
- Backup and Migrate - Drupal 6, Drupal 7
- Better Exposed Filter - Drupal 6, Drupal 7
- Boost - Drupal 6, Drupal 7
- Commerce - Drupal 7
- Composer Manager - Drupal 6, Drupal 7, Drupal 8
- Context - Drupal 6, Drupal 7
- Chaos Tools - Drupal 6, Drupal 7
- Diff - Drupal 6, Drupal 7
- Display Suite - Drupal 6, Drupal 7
- Devel - Drupal 6, Drupal 7
- Features - Drupal 6, Drupal 7
- Global Redirect - Drupal 6, Drupal 7
- Google Analytics - Drupal 6, Drupal 7
- ImageCache - Drupal 6, Drupal 7(Built-in)
- Internationalization - Drupal 6, Drupal 7
- jQuery Update - Drupal 6, Drupal 7
- LoginToboggan - Drupal 6, Drupal 7
- Metatag - Drupal 7
- Module Filter - Drupal 6, Drupal 7
- Nodequeue - Drupal 6, Drupal 7
- Pathauto - Drupal 6, Drupal 7
- Rules - Drupal 6, Drupal 7
- Search Krumo - Drupal 7
- Strongarm - Drupal 6, Drupal 7
- Ubercart - Drupal 6, Drupal 7
- Views - Drupal 6, Drupal 7, Drupal 8(Built-in)
- Webform - Drupal 6, Drupal 7
- XML sitemap - Drupal 6, Drupal 7
Here are some other awesome special modules for specific purposes
Great tools for drupal:
- Drush - A command line shell and scripting interface for Drupal
Distributions for your special needs:
- Acquia Drupal - Distribution of the open source Drupal social publishing system
- Commerce Kickstart - Ecommerce distribution running with Drupal commerce module
- Julio - A distribution for Schools, School Districts, and University Departments
- Open Deals - Deals site distribution based on Drupal 7
- Open Hotel - Create a full featured Hotel site with online booking and online availability
- Recruiter - Distribution for building Drupal based e-recruitment platforms
- Restaurant - Everything you need to kickstart your restaurant website
- Spark - Enhanced Drupal authoring experience
- Wiki installation profile - Wiki with Drupal
Useful slideshows:
- Drupal Code: Day 1
- Drupal Code: Day 2
- Using Features
- Drupal Deployment
- Drupal Association YouTube Videos
Tutorials and articles:
- The Drupal Cookbook
- Web Omelette Drupal Tutorials
- OSTraining Drupal Tutorials
- Authenticated User Caching
- 8 Answers for All Drupal 6 Site Owners
- Useful Theme Snippets For Drupal 7
- Your Drupal site got hacked. Now what?
- Drupal Security Tips for Developers
- Drupal Watchdog Issues
- Drupal 8 Ready: What's new for Developers?