Optimization

1. WP Super Cache

2. WP-Optimize

3. W3 Total Cache

Forms

1. Contact Form 7

2. Fast Secure Contact Form

3. Gravity Forms (Premium –  $39)

4. AJAX Contact Forms (Premium – $10)

Comments

1. Disqus Comment System

2. GD Star Rating

3. Wizzart – Recent Comments

4. Facebook Comments

5. Thank Me Later

6. Disable Comments

7. WP Customer Reviews

Site Backup

1. WP-DBManager

2. BackUpWordPress

Posts

1. Editorial Calendar

2. Yet Another Related Posts Plugin

3. SimpleReach Slide

4. WordPress Popular Posts

5. Raw HTML

6. Auto Post Thumbnail

Security

1. Akismet

2. SI CAPTCHA Anti-Spam

3. Secure WordPress

4. BulletProof Security

Design & Theme Customization

1. Widget Context

2. WP Google Fonts

3. WP Maintenance Mode

4. Genesis Simple Sidebars

5. Shortcodes Ultimate

6. All In One Favicon

7. Font Uploader (Premium – $10)

8. WPtouch

9. Widget Logic

10. WP Content Slideshow

Media

1. Easing Slider

2. NextGEN Gallery

3. flickrRSS

4. WordPress Video Plugin

5. oQey Gallery

6. uBillboard (Premium – $20)

7. WP Lightbox 2

Commerce

1. WP e-Commerce

2. Jigoshop

3. WooCommerce

4. uPricing (Premium – $15)

5. PayPal Donations

SEO

1. All in One SEO Pack

2. WordPress SEO by Yoast

3. Google XML Sitemaps

Social

1. Add Link to Facebook

2. WP to Twitter

3. Digg Digg

4. ShareThis

5. BuddyPress

6. bbPress

7. The Google+ plugin

8. Twitter Widget Pro

Marketing

1. Newsletter

2. WP125

3. s2Member

4. MailPress

5. Subscribe2

6. MailChimp Widget

7. Simple PopUp

Miscellaneous

1. WP-PageNavi

2. Jetpack by WordPress.com

3. Exclude Pages

4. Broken Link Checker

5. ManageWP Worker

6. Redirection

7. FD Feedburner Plugin

8. Hotfix

9. Google Analytics for WordPress

10. WP-Polls

11. Ozh’ Admin Drop Down Menu

12. Pretty Link Lite

13. 5sec Google Maps (Premium – $8)

14. Advanced Access Manager

Extensive Roundup of the Best WordPress Plugins You’ll Ever Need: Year 2012 Edition.