I've given this presentation several times and it always changes. This particular session was 1.5 hours long so I was able to cover more plugins than ever.

1. 20+ WordPress Plug-Ins to Rock
Your Blog or Website
Cindy Meltzer
The Social Craft
@cindymeltz

2. Plugin Basics
• What are plugins?
• Wordpress.com vs. Wordpress.org
• How to find and install plugins

3. Mobile Friendly
• WP Touch
• A responsive theme

4. Slideshows
• Slidedeck 2 (lite and paid)
• vSlider
• Nivo Slider (paid)

5. Contests
• Social Campaigns
• And the Winner Is
• Rafflecopter

6. Social Sharing
• Shareaholic
• Digg Digg
• Pinterest Image Pin

7. Related Content
• nRelate Related Posts & Popular Posts
• YARPP (Yet Another Related Posts Plugin)
• Wordnik

8. Social Media Feeds
• Instapress
• Pinterest Pinboard Widget
• Tweet Blender

9. Comments
• Commentluv
• Disqus
• Livefyre

10. Ecommerce
• Ecwid
• WooCommerce

11. Events
• The Events Calendar
• Eventbrite Tickets add-on

12. Admin Tools
• Editorial Calendar
• Adminimize

13. Content & Images
• Zemanta
• InboundWriter
• PhotoPin (website)

14. Spam and Hackers
• Akismet
• Sucuri

15. Speed
• Quick Cache
• WP Smush.it

16. SEO
• Yoast SEO
• Broken Link Checker

17. Analytics
• Google Analytics for Wordpress
• Google Analytics Dashboard
• Quicklytics (app)

18. General Tips for Choosing Plugins
• Compatible with latest version of WordPress
• Number of users in the thousands
• Last updated within 6 months
• Active support forum
• Premium plugins are often worth the money
• Host recommendations (wp engine)

19. Backup
• Wp backup