enomoto celtislab

You are using a tag cloud of the standard, and you do not want to display tags that belong to the category not related to the article. 
Try this widget. 
Based on the category of the display article, this widget gets the tag from the article categories of related range. 
For the article there is no category of post page, etc., or by setting <code>all category</code>, <code>internal link article</code>, it displays the tag by examining the related category. 
If you check the ‘internal link article’, get a category from the internal links to articles.
Select Category related range
<ul>
<li>All Category (unrelated article)</li>
<li>Current article Category</li>
<li>Include child category tree</li>
<li>Include parent category tree</li>
<li>Include internal linked article Category</li>
<li>Exclude Category</li>
</ul>
Other parameters : Display format, Sort by, Order, Font size, Number of tags to display, …
<a href="http://celtislab.net/wp_plugin_DCTagCloud/" title="Documentation in Japanese" rel="nofollow ugc">日本語の説明</a>

DynamicCategoryTagCloud

Displays the tag cloud dynamically from related articles belonging to the category of the display article

azurecurve

The plugin integrates with the standard WordPress tag cloud, but allows tags to be excluded and easy control of other settings such as min and max font sizes, the sort order and number of tags to include.
This plugin is multisite compatible.
This plugin supports language translations. If you want to translate this plugin please sent the .po and .mo files to development.translations@azurecurve.co.uk for inclusion in the next version (full credit will be given). The .pot fie is in the languages folder of the plugin and can also be downloaded from the plugin page on http://development.azurecurve.co.uk.

azurecurve Tag Cloud

I love Software which intelligently uses already available resources - in this case, the WordPress Tag-Cloud function, with all the options provided by the function but not settable in the standard widget. Sure there are other tag cloud plugins out there, but in comparison to this one they are sure going to bloat your frontend code!

A great boon for MultiSite users is that this plugin offers global settings in the network admin area. Then each site can either opt to use those, or set its own. Now that's really sweet!

Finally, the support from Ian, the author, has been superb - fixes done within hours even at the weekend! For my part I pronounce the new version "bug free" and was glad to help polish a great product.

Thanks Ian!



Minimalistic way for a nice Tag Cloud, own MultSite options

Displays a tag cloud with easy control of settings and exclusion of tags from the cloud.

DynamicCategoryTagCloud vs azurecurve Tag Cloud