Below are the Top Ten Joomla Extensions

1. JCE (Joomla Content Editor)

Joomla Content Editor (JCE) is probably one of the most popular Joomla extensions. Specially for those who might not be technically inclined or have issues using the default Joomla page editor. JCE is a What You See Is What You Get (WYSIWYG) editor. This means that youre able to edit your pages without any HTML skills at all. Some of the features that JCE adds to the Joomla page editor include:

a) Font selection
b) Background color
c) Multimedia management
d) Import from Microsoft Word

URL:-http://extensions.joomla.org/extensions/extension/edition/editors/jce

2. SH404SEF

This extension Properly optimizing your site so that it ranks highly in search engines such as Google and enables you to bring in more traffic to your site naturally. Unfortunately Joomla doesnt include too many tools for SEO. therefor this extension specifically to make up for that downfall. Some of the SEO elements handled by this extension are:

a) Remove duplicate URLs
b) Re-write URLs
c) Customize page titles and descriptions
d) Heading tags (h1, h2, etc.)
e) Caching
f) Custom 404 pages
g) Mobile redirect
h) Social media sharing

URL:-http://extensions.joomla.org/extension/sh404sef

3. Akeeba Backup

This extension is probably one of the most widely used backup extensions for Joomla. It creates a complete backup, restoration and site migration solution for your Joomla sites. With this extension, you have the ability to control what files you want to backup. With just a few clicks you can completely automate the entire process which is a necessity for any backup extension. You can have your backups to the Cloud as well so that you can access it anywhere.
Most important feature of Akeeba Backup is rollback which will recover your site back to a point .
Features are:-
a) Backup your entire site and its database with a single click
b) Restoration script included in the backup archive
c) Direct server-to-server transfer of your site over FTP/FTPS (DirectFTP) or SFTP
d) Restore your backup files from within the component
e) Option to exclude non-Joomla! database tables
f) Administer your backup files (download, delete) g)Send backup archives to yourself by email

4. Chronoforms

Chronoforms provides the facility to add custom forms to your Joomla site. It provides features such as field creation, processing emails, and captcha support. Using this extension you can create any type of form like registration/login forms, article submission forms, contact form and many more.
Create form in three quick steps:
a) Create form html using editor
b) Copy html code Result.
c) Paste the code into your ChronoForms 'Form Manager' and save.

Features:-
a) Ability to use Javascript and CSS styles code in the form
b) Drag and Drop form creation wizard for quick forms creation
c) Add Captcha imageverification to your form to protect you from Spam. d) setup Javascript fields validation
e) Easy to add Server side validation
f) Ability to create DB tables and connect to any table to save or update its records,

URL:-http://extensions.joomla.org/extension/chronoforms

5. virtuemart-Online shopping cart

Virtuemart extensions provides shopping cart to your Joomla site, you should seriously consider Virtuemart as it has most important shopping cart features which we always require while making e commerce sites such as currency conversion,order history for the customers,ratings and comments on product, downloadable products and lots more. It provides facility for most payment gateways such as Paypal, Authorize.net and 2Checkout.

URL:-http://virtuemart.net

6. K2

K2 was created to provide facility to handle your content much easier than default joomla provides to us Using this extension user will have facility to create an online magazine, directory sites etc. just install the extension using extension manager , and then import all of your Joomla articles and work with K2 to get more features such as:

a) Article image management
b) Video management
c) Image gallery management
d) Comments
e) Tags
f) Content modules
g) Drag and Drop Media Manager

URL:-http://extensions.joomla.org/extensions/extension/authoring-a-content/content-construction/k2

7. Xmaps

Xmaps is a requirement for an easy to submit sitemaps for Google Webmasters / Bing Webmasters. The system allows you to configure how you want to share your pages with Google's crawler.Xmaps also requires plugins based on how you are managing content. If you are using K2, you'll need to get the K2 plugin for Xmaps.It allows sites to create both front-end and XML sitemaps based on the existing structure of your menus.

8. ccNewsletter

This extension allows you to completely manage your own newsletter right inside Joomla.Its extremely user friendly so that anyone with or without technical skills can jump in and develop their first list.

Features:-

a) Creating and sending your newsletter
b) Utilize newsletter templates
c) Terms and Conditions acknowledgement
d) Visitors can see newsletter archives from your site
e) Import email addresses from txt, csv, or text area
f) Export your email subscribers to csv

URL:-http://extensions.joomla.org/extensions/extension/marketing/newsletter/ccnewsletter

9. Social Share and Vote Button

Social Share/Vote Button is a popular Joomla plugin that display social share or vote button in articles / content. It contains most of the popular social networks or share/bookmark sites that supports button/badge for vote/share.Using this extension you can share your content very easily on most of the popular social networking sites without any trouble

URL:-http://extensions.joomla.org/extensions/extension/social-web/social-share/social-share-and-vote-button

10. Mobile Joomla

Mobile Joomla! is the best way to mobilize your Joomla! site, displaying beautifully on iPhone, iPad, Android, Windows Phone and all other phones.Mobile Joomla! is also the easiest way to speed up your responsive template performance up to 400% on mobile devices. This extension will work for all mobile devices and it display differently on each and every device Using this you can create mobile friendly site very easily.Always prefer this extension when there is a requirement to convert existing site into mobile friendly site.

URL:-http://extensions.joomla.org/extensions/extension/mobile/mobile-display/mobile