This plug-in provide tag cloud.
$ cd APP_ROOT/public/plugins/
$ git clone git@github.com:daic-h/lokka-tag_cloud.git
e.g.
<% tag_cloud :classes => %w(level1 level2 level3) do |tag, css_class| %>
<%= link_to tag.name, tag.link, :class => css_class %>
<% end %>
If you would like to sort by tag.name
<% tag_cloud :classes => %w(level1 level2 level3), :sort => true do |tag, css_class| %>
<%= link_to tag.name, tag.link, :class => css_class %>
<% end %>