Renoun is very new onto the scene and hasn't yet left beta. It's a Twitter based search engine, and although I've seen comparisons to Topsy, (RIP) I think it's rather different. You start by discovering new content. The results page is in the fairly common tile/magazine format that we see so often these days:
and you can click on any of the tiles to get more information as to how often the story has been shared, and across which social media platform:
You can also click directly onto any of the links and share it yourself. Search results can be filtered by time - 6 months, 3 months, 2 weeks or 'now'. You can also check out a list of influencers, which seems to be a list of people who talk about the subject arranged in follower # which is a bit limited and clunky, but it could be helpful in some circumstances. A list of publishers is also only a click away and if you click on either a publisher or an influencer you can then get more information about them directly as well, so if you're looking for experts in a particular area, this is a good tool to help identify them.
It's a nice engine, and worth taking a look at.