When I make bar charts, is there a way to have the X-axis hidden so that the bars look like they are floating?

In order to hide an axis, select it, and then choose Change/Selected Object. Then set the color of the axis to match the color of the plotting area of your graph.

For example, if you have a white plotting area, change the color of the axis to white. To make your bars look the best when you do this, you should make them solid-color fills with no outline. This works with bar graphs created for one-grouping-variable or two-grouping-variables.