Web 2.0 is the general term for new technologies, applications and services that enable users to interact and personalize websites. The derivative term Library 2.0 was proposed in the mid-2000s. This article reviews how public libraries have made attempts to renew their services by adopting Web 2.0 technologies. The research material mainly consists of articles and reports discussing the developments of Library 2.0. In addition, the study makes use of data obtained from the websites of public libraries that have pioneered in the field of Library 2.0. The study identified four main purposes for which public libraries have adopted Web 2.0 technologies: communication, content sharing, social networking, and crowdsourcing. To serve the ends of communication, public libraries have adopted technologies such as RSS feeds and short messaging. The needs of content sharing are primarily served by using blogs and content sharing sites such as YouTube. Public libraries have also used Web 2.0 technologies to support social networking. Finally, to advance crowdsourcing, public libraries have mainly used tagging functionalities and systems of book rating. Overall, the findings indicate that experiences gained from the utilization of Web 2.0 applications are fairly positive and are thus encouraging for the development of Public Library 2.0.