One of the most visible trends on the Web is the emergence of Social Web sites, which help people create and gather knowledge by simplifying user contributions via blogs, tagging and folksonomies, wikis, podcasts, and online social networks. Current online-community sites are isolated from one another, like islands in a sea. Various discussions might contain complementary knowledge and discussions—parts of the answer a person is looking for—but people participating in one discussion can't readily access information about related discussions elsewhere. The potential synergies among many sites, communities, and services are expensive to exploit, and their data are difficult and cumbersome to link and reuse. The main reason for this lack of interoperation is that for the most part in the Social Web, common standards still don't exist for knowledge and information exchange and interoperation. However, the Semantic Web effort aims to provide the tools needed to define extensible, flexible standards for this purpose. The Semantic Web technology stack is well defined, enabling the creation of metadata and associated vocabularies. The Semantic Web effort is in an ideal position to make Social Web sites interoperable. Applying Semantic Web frameworks including SIOC (Semantically Interlinked Online Communities) and FOAF (Friend-of-a-Friend) to the Social Web can lead to a Social Semantic Web, creating a network of interlinked and semantically rich knowledge. This article is part of a special issue called Semantic Web Update.