NCTM's Illumination site offers a free Bar Grapher Tool students may use to create a bar graph of their own data. Students simply input the data, select appropriate minimum and maximum values, width of bars, color of bars, then click on Graph Data to create a bar graph.
The graph to the left represents one trial of Mathwire's Cereal Toy Applet.
This is a useful tool for the math classroom. Once students know how to create a bar graph with all of the necessary components, the emphasis moves more toward the analysis of results. Allowing students to use real-world graphing applications provides more time for discussion and analysis of group results.
Check out the Bar Grapher Tool on the NCTM Illuminations site.