Excel is still a commonly used platform for data visualization, especially for those in business, marketing, economics, and finance. Duke University Libraries provides an introduction to the visualization capabilities of Excel.
RAW Graphs is a free and open source tool for data visualization. an online platform to make data visualizations. Users can select graph type (i.e., scatterplot, bar chart, dendrogram, etc.) based on type of input data (i.e., numeric, categorical).
Gephi is a free software for visualizing networks, comprised of "nodes" and "edges". "Like Photoshop but for graph data, the user interacts with the representation, manipulate the structures, shapes and colors to reveal hidden patterns."
Voyant Tools is a web-based text reading and analysis environment. It is a scholarly project that is designed to facilitate reading and interpretive practices for digital humanities students and scholars as well as for the general public.