Andreas Norman

This widget that displays an archive for the current selected category. On non-category pages a standard archive is displayed.
<ul>
<li>On a post page the widget will only display an archive for posts in that category</li>
<li>On a category listing the widget will only display an archive for posts in that category</li>
<li>On the front page or in a search result or any other page that doesn’t reside in a category a standard archive will be displayed.</li>
</ul>

Subzane Categorized Archive Widget

A widget that displays an archive for the current selected category. On non-category pages a standard archive is displayed.

Hiroshi Sawai

This Plugin adds <code>Category Monthly Archives</code> to Widget. 
Added widget displays category monthly archives links on category page. 
Only displays links on category page.

Category Monthly Archives

This Widget display category monthly archives links on category page.

Subzane Categorized Archive Widget vs Category Monthly Archives