The purpose of this study was to investigate how federated search engines are incorporated into the Web sites of libraries in the Association of Research Libraries. In 2009, information was gathered for each library in the Association of Research Libraries with a federated search engine. This included the name of the federated search service and the presence, placement, and context of federated search boxes and links on library home pages, secondary pages, electronic resource lists, research guides, and course pages. Information was also gathered to compare whether the context of the federated search engine matched the resources included. During this study, a number of Web site redesigns affected how federated search engines were incorporated. A few of these site changes are described to illustrate the evolving nature of federated search engines on library Web sites. Building on a previous study, this study identified an increase in the number of libraries in the Association of Research Libraries with federated search engines. The findings also reveal a common problem of mismatching federated search context to the resources included, which has significant implications for users. Based on the observations of this study, a few best practices are provided to aid libraries in evaluating or reevaluating how federated search engines can be incorporated into their Web sites. (Contains 3 tables.)