View Module : How to display list of Taxonomy terms with record count
Drupal 7

With View 7.x-3, you first remove the "Content: Title" contextual filter, and then you add the "Content: Has taxonomy term ID" one.

In the dialog for the settings that appear once you select the context filter, you set the options as in the following screenshot. There are two displays: "Page," and "Attachment"; the first screenshot is for "Page."





The result is the following view; the first screenshot show the output when none of the links have been clicked on.





Drupal 6

In Views 6.x-3, the used terminology and the user interface change, but the steps to follow are similar.

Also in this case, there are two displays, which have the same name used in Views 7.x-3; differently from Views 7.x-3, the display to change are the default one, and "Attachment."

You first remove the "Node title" argument, and add the "Taxonomy: Term ID" argument; the first image is for the default display.





In the latter display, the argument will be displayed as list by default; I didn't change it.

Important: There are two similar contextual filters/arguments, where in one appears the word "depth"; the difference is that this last contextual filter/argument shows all the node where the taxonomy term is the select one, or one of its children. You should use this one, if the vocabulary is organized hierarchical, and for example, the taxonomy terms are "Porsche," "Porsche >> Carrera," and "Porsche >> Cayenne"; in this case, selecting "Porsche" will show also the nodes using  "Porsche >> Carrera" and "Porsche >> Cayenne."