DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
talkatv - talkatv is an open source comment service much like ...
Commento - A fast, bloat-free comments system to foster discussion on your website
utterances - A lightweight comments widget built on GitHub issues.
UpContent - UpContent is a content discovery tool that helps businesses to drive meaningful conversations with their audiences.
JustComments - Easy to set up, ad-free and reliable comment system