Javier López Úbeda

This widget add a tag cloud 3d to your sidebar.
Based on the jquery plugin tagcanvas.js from http://www.goat1000.com/.

The Krotek

Customizable widget and shortcode to display tag cloud anywhere you want. You can use it as standard tag cloud widget, as shortcode in any post or page, or both ways. Tons of options allow you to fine tune cloud layout to your needs.
STANDARD FEATURES
<ul>
<li>Display list of post, category or link category tags.</li>
<li>Define number of tags to be displayed.</li>
<li>Set custom tag separator.</li>
<li>Select tag taxonomy: posts, categories or link categories.</li>
<li>Choose cloud mode: shortcode only, widget only or both.</li>
</ul>
PREMIUM FEATURES
<ul>
<li>Define smallest and largest tag size.</li>
<li>Select size unit: px, pt, em or percent.</li>
<li>Choose layout: standard flat cloud or unordered list.</li>
<li>Order tags by name or count.</li>
<li>Sort tags ascending, descending or randomize.</li>
<li>Define list of tags to exclude from cloud or include only.</li>
</ul>
You can purchase Premium version <a href="https://thekrotek.com/wordpress-extensions/tag-cloud" rel="nofollow ugc">here</a>.

Custom Tag Cloud

...but it at least is a little better than the one that comes with WordPress.

Free version is not very customizable...

Customizable widget and shortcode to display tag cloud anywhere you want.

Tag Cloud Canvas vs Custom Tag Cloud