George Stephanis

Sure, WordPress has a widget for displaying your most recent posts, but what if you want to only display the posts from a single category in a widget, and not everything? This plugin Widget lets you set the title, category, and quantity of posts to display, then it kicks out a list of the most recent posts in that category.

Recent Category Posts Widget

This widget will let you display a list of the most recent posts in a single category in your sidebar.

javierjara

This plugin adds a simple widget that you can customize easily it allows you to display a number of recent blog posts from a specific category. You have the options to choose a title, category, number of posts and whether or not to show the post date or to show the image featured (Post Thumbnails).The posts will be ordered by date just like the default Recent Posts widget included with WordPress. 
check the category you want to show.

Custom Recent Posts Widget Plus

Nice widget it is like the default Recent Posts widget except you can choose a category and in addition show the thumbnails.

Recent Category Posts Widget vs Custom Recent Posts Widget Plus