Disqus is still one of the best comment systems available for WordPress (despite past controversies). In fact, many top WordPress sites rely on it to manage reader discussions. The service is pretty easy to get started with. These Disqus plugins let you get more out of it:
Disqus Conditional Load: this plugin lets you choose how to load Disqus comments. It also offers useful features such as lazy loading.
Disqus Notify Post/Page Author: notifies post/page authors by e-mail of comments posted through Disqus.
Super Socializer: provides you with social login, commenting, and sharing. Lets you use Facebook, Disqus, or other comment systems.
Custom Comment Form Title: a simple plugin that lets you change the title above the Disqus comment system. The plugin is compatible with Genesis.
Disqus Recent Comments Widget: adds a recent comments widgets for Disqus to your website. You can control avatar size, except length, and other settings.
Have you found better plugins for Disqus? Please share them here.