Pearltrees is a social bookmarking tool that allows people to organize links and information visually into a web of interconnected nodes.
Here's how their site describes it:
Pearltrees is a collaborative network that let users create, enrich and share the world of their interests. We call it a human-powered interest network because its content is made and organized by its community. In Pearltrees, everyone creates its world and uses parts of others' worlds to extend it. By doing so, everyone contributes to the overall project: building the first human organization of the Web.
