Web 2.0 tools allow for user-generated content and multi-sensory communication on the evolving, collaborative web. This has implications for libraries to become more socially rich and user-centric online communities. The document discusses several Web 2.0 tools like blogs, wikis, microblogging and social bookmarking that libraries can use to engage users and create a Library 2.0 environment that is user-centered, multimedia, socially rich, and communally innovative. Concerns about the time and effort required by libraries are noted.