+Gabriel Vasile has put together a great list of the top 25 most popular Chrome extensions and apps for Google Plus
1. Extended Share (75,616 users) - http://goo.gl/mijZv
Extends Google+ to share to Facebook, LinkedIn, Twitter, and many more.
2. +Photo Zoom (60,487 users) - http://goo.gl/rHIEP
Easily zoom photos and profile pics from your Google Plus Stream.
3. Facebook Friend Exporter (51,651 users) - http://goo.gl/MFNy3
Get your data contact out of Facebook to Google Contacts or CSV, whether they want you to or not.
4. Scroll To Top Button (41,868 users) - http://goo.gl/1KFqm
Adds a scroll to top or bottom button.
5. Replies and more for G+ (39,957 users) - http://goo.gl/Zv8WJ
Adds reply and reply-to-author buttons to Google+ comments and a number of other enhancements.
6. Surplus (37,774 users) - http://goo.gl/vRlPE
Google Plus Integration for Chrome
7. G+me (35,532 users) - http://goo.gl/JgR2Z
Collapses the Google+ stream while keeping live updates: collapses posts, hides comments, etc.
8. Google Translate for G+ (26,898 users) - http://goo.gl/PjSrQ
Translate your Google+ stream using integrated, inline, Google Translate support.
9. Usability Boost for G+ (26,301 users) - http://goo.gl/CLnUG
Greatly improves readability on Google Plus, ability to star posts to read later and some other useful features
10. Google+ Ultimate (16,759 users) - http://goo.gl/Q6xd3
This extension for Google Plus adds functionatility and themeing for the site.
11. Google Plus Directory (13,618 users) - http://goo.gl/iAdXC
Find your G+ is a Google Plus person directory, where you can meet new people, start making new friend circles and more for Google+
12. -1 Minus One for G+ (12,274 users) - http://goo.gl/WYuf6
Minus one (-1) button in Google+ (Post & Comment), Notifications.
13. More for Google Plus (7,996 users) - http://goo.gl/JzwVL
Loads more content as you reach the bottom of the Google+ page.
14. Google+ Tweaks (7,601 users) - http://goo.gl/x00Pw
Tweaks to the layout and features of Google+ (Google "Plus") Full width, thumbnails only, etc.
15. Notification Count for G+ (7,487 users) - http://goo.gl/Zml0f
Extension for displaying unread notification count for Google Plus
16. Helper for Google+ (7,136 users) - http://goo.gl/lNbSX
Add extra functions the Google+. Get desktop notifications on new posts. Share Posts via twitter. Translate posts with Google Translate. Bookmark posts faster for reading later (also to delicious.com). Linked #hashtags. Search in posts and profiles directly from your omnibox.
17. G+ Count in Title (5,411 users) - http://goo.gl/dANji
Adds notification count to the document title in the page tab.
18. +1 Button (5,256 users) - http://goo.gl/h67bs
Plus one every page you like with only one click, directly from omnibox, without any annoying popup
19. Uncircle+ (5,022 users) - http://goo.gl/VqDLu
Google+: Find and Remove Inactive People in Selected/All Circles. Inactivity = No Public/Private Posts At All or Since a Chosen Date
20. +Everything (4,590 users) - http://goo.gl/0lYlx
Adds the Google+ bar to all websites.
21. Auto-Colorizer for G+ (4,220 users) - http://goo.gl/kRbLi
Colorizes Google+ and Facebook based on the user's photo.
22. Google Plus Friend Finder (2,803 users) - http://goo.gl/rTcEZ
Google Plus Friend Finder it's a web application wich helps you to find your friends by city, country, occupation and even more.
23. G+ Stream Pause (2,600 users) - http://goo.gl/tKSFC Allow's you to pause your Google+ stream so you can take your time reading or watching videos posted
24. Golden View for Google+ (1,275 users) - http://goo.gl/scoaD
Google Plus enhancements: (optional) modules: User Mute, Default Circle, Hide Images, Hide comments, & Search w/ Google.
25. Hangout Auto Try Again for G+ (1,066 users) -http://goo.gl/sQkAx
Tired of clicking the try again button for Hangouts? Then install this.
Gabriel's original post is here
(via +Denis Labelle)