Jess

Thumbnail Updater does exactly what it’s name implies: it updates thumbnails. WordPress 2.9 introduced support for 
post thumbnails but one problem is that the support is not backwards compatible—meaning that if you downloaded or created 
a theme that supports post thumbnails, any images uploaded prior to the activation of that theme will not have the new thumbnail size.

Thumbnail Updater

A plugin for updating your thumbnails whenever a new thumbnail size is added with add_image_size()

msakib

A simple and nice plugin to Smpale Latest Post widget

Latest Posts

Latest posts widget to display recent posts

Thumbnail Updater vs Latest Posts