Scoopler is a real-time search engine. We aggregate and organize content being shared on the internet as it happens, like eye-witness reports of breaking news, photos and videos from big events, and links to the hottest memes of the day. We do this by constantly indexing live updates from services including Twitter, Flickr, Digg, Delicious and more. When you search for a topic on Scoopler, we give you the most relevant results, updated in real-time.
via Mr. Byrne
OneRiot crawls the links people share on Twitter, Digg and other social sharing services, then indexes the content on those pages in seconds. The end result is a search experience that allows users to find the freshest, most socially-relevant content from across the realtime web.
via Mr. Byrne
StumbleUpon is a big network that has actually millions of users. People all over the place are using this resource as a strategy to grow their online traffic.