Disqus and Cackle have CMS integrations with Joomla. Disqus integrates the popular Disqus comments system & service into any Joomla based website. Disqus (pronounced as discuss) is a service and tool for web comments and discussions and is currently the most popular comments-as-a-service provider worldwide. It makes commenting easier and more interactive, while connecting websites and commenters across a thriving discussion community.
To make Disqus work, download the Disqus for Joomla plug-in. On your Joomla admin, select Extension Manager and upload the Disqus plugin. Under the Extensions menu choose Plug-in Manager and in the Disqus subdomain field, enter your shortname, and you are good to go.
Plugin comments for Joomla is also available for comment from Cackle, which allows you to leave comments after authentication through the most popular social networks: VKontakte, Google+, Facebook, Twitter, Yandex, LinkedIn, Live Journal, Tumblr, Dropbox, Foursquare, Instagram, Live, 500px, Stackoverflow, Yammer, Soundcloud.
Using Cackle comments for the site increases attendance by attracting new users through social networks (crossposting) and search engines (indexed), reduces the load on the site through the use of a cloud service, and instead of the dull standard comments, you have a beautiful and powerful solution to create active communities.