One of the most requested gadgets for Blogger was the Label Cloud (or tag cloud). Previously, the label gadget showed a list of labels:
Users can also select which labels to be displayed:
To add this tag cloud to your blog, log-in and in your Blogger Dashboard: Layout > Page Elements, click on "Add a Gadget" where you want the tag cloud to be displayed, then select "Labels" from the Basic gadget list. P.s.: don't forget to check the "Cloud" box in the labels options!