George Stephanis

Just a little widget that adds in some useful functionality that WordPress (oddly enough) doesn’t include stock … listing almost all of your categories. Say, for example, you have a utility category entitled “Events,” and you want to display a list of all your site’s categories, but don’t want “Events” to display in that list. Instead of hard-coding a list into a text widget, just use this!

Almost All Categories Widget

This widget will let you display a category list in your sidebar, excluding any categories that you would like.

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.

Almost All Categories Widget vs Custom Recent Posts Widget Plus