This talk will present two research projects under way in the Network and agents Network (NaN), which study ways of leveraging online social behavior for better Web search. GiveALink.org is a social bookmarking site where users donate their personal bookmarks. A search and recommendation engine is built from a similarity network derived from the hierarchical structure of bookmarks, aggregated across users. 6S is a distributed Web search engine based on an adaptive peer network. By learning about each other, peers can route queries through the network to efficiently reach knowledgeable nodes. The resulting peer network structures itself as a small world that uncovers semantic communities and outperforms centralized search engines.