Many states and local districts use career clusters as a means of broadening the focus of secondary education, particularly career and technical education, as preparation for both further education and work. One continuing trend in career clusters is sheer variety. Cluster frameworks vary in the number, nomenclature, and organization of clusters. Career clusters are used not only for organizing instructional programs and curricula but also for structuring career exploration and planning. Other issues in career clusters include crosswalking across cluster frameworks; outcomes; integrating academic, technical, and employability standards; and providing information on occupations included in clusters. The major portion of this publication consists of an annotated bibliography of 21 resources. (YLB)