Arno Welzel

This widget displays top level categories in multiple columns.
After installation, just add the widget to desired sidebar or footer and optionally enter a custom title and the number of columns to be displayed.
By default two columns are used, but you can set any number of columns you like in the backend.
Also see details at <a href="http://arnowelzel.de/wp/en/projects/wordpress/multicolumn-category-widget" rel="nofollow ugc">http://arnowelzel.de/wp/en/projects/wordpress/multicolumn-category-widget</a>.

Multicolumn Category Widget

This widget displays top level categories in multiple columns.

MrXHellboy

This WordPress plugin (widget) will be shown when visitors are viewing a single post, category page or both. Otherwise, it wont be there at all. 
The widget contains a list of post titles from the same category(s) the visitor is viewing the post from, so the visitor is able to swiftly change posts by clicking on the titles shown. 
Posts published in multiple categories are taken care of just fine. I’ve introduced a new feature in version 1.6 which gives you the possibility to show all the categories the post has been published in or the category where the visitor has been spotted the last time(uses cookie).
The widget can be controlled with the following widget options:
<ul>
<li>Title (before the category name(s))</li>
<li>Exclude category(s) by ID</li>
<li>Exclude categories on: Single, Category, Both, None</li>
<li>Sticky posts on top: Yes | No</li>
<li>Show posts from year: a specific year or all years</li>
<li>Show widget on: categories | single posts | both</li>
<li>Show category title(s): Yes | No</li>
<li>Post has multiple categories – what now: Show all categories | Show the last category viewed</li>
<li>Show how many posts</li>
<li>Single posts view – Order: DESC | ASC</li>
<li>Single post view – Orderby: Author | Category | Date | ID | Random</li>
<li>Category view – Order:?DESC | ASC</li>
<li>Category view – Orderby: Author | Category | Date | ID | Random</li>
<li>Remove/Keep child categories</li>
</ul>
<h3>Development Blog</h3>
<a href="http://online-source.net/category/scripts/wordpress-plugins/" title="Online-Source WordPress plugins" rel="nofollow ugc">Online-Source WordPress plugins</a> 
<a href="http://online-source.net/forums/forum/support/wordpress-plugins/" title="Support forum" rel="nofollow ugc">Support forum</a>

Category Content

This Wordpress plugin (widget) will be shown when visitors are viewing a single post, category page or both. Otherwise, it wont be there at all.

Multicolumn Category Widget vs Category Content