In an age characterized by tremendous technological break-throughs, the world is witnessing overwhelming quantities and types of information. Digital Libraries (DLs) are a result of these breakthroughs, but they have not been spared by the challenges resulting from them. While DLs stakeholders are still struggling to come to terms with the massive quantities and complex types of information, the needs of the digital library as an information/knowledge environment is still evolving including new challenging needs. Information Visualization (Infovis) represents a viable solution to this. The human-vision channel has a high bandwidth and it can surveil a visual field in a parallel manner, processing the corresponding data to different levels of detail and recognition and understanding of overwhelming data can be done at an instant. It is an outstanding resource that can be exploited within a DLs in order to address issues arising from the conventional needs (such as the quantities and types of information) and the non-conventional needs. Here we analyze Infovis as a resource for DLs, relating visualization techniques to specific DLs needs, providing a classification of Infovis techniques and reporting about our analysis of DLs tasks and their correspondence with suitable visualizations.