This plugin is designed to perform some simple class-based widget framework in wordpress. Using it you can write widget classes (or extend some) in object oriented manner. 
There is a simple widget API, defining basic interfaces and classes. AJAX is core-embedded. After writing your class, you must install it (this is done for the purpose of writing custom database data needed for widget functionality) in order to define widgets of this class. After defining widgets you can place them directly to your page using wordpress shortcodes or special plugin function. You can specify skin (special markup) for each widget placement. You can also define containers (or sidebars) and place widgets into them. Containers are also placed on pages using shortcodes or function call.

Mind3doM RyeBread Widgets

Allows to extend your blog with class-based skinnable ajax-featured widgets, optionally arranged in page areas (containers).

Alan Hidalgo Pagoto

polvodigital

A plugin which allows you to put posts of a specific category (you can use even all the categories) in a widget. You can use more that one widget at the same time and configure different time transictions between two posts. You’re able to change the quantity of posts in each widget as well. When there are too many posts to be loaded, the plugin loads the first ten and, when the first transiction is triggered (between the first and the second posts) the 11th is loaded and put in the queue. When the second transiction is triggered, the 12th post is loaded and the plugin keeps doing it until all posts are loaded. When it happens, the plugin stops making ajax requests to the server and the page runs normally.
You can find a demo on http://www.polvo.com.br/plugins/post-content-slider. There are two widgets configured on the right. The first one is set to change the post every 4 seconds and the second one every 10 seconds.
<h3>Files structure</h3>
plugins/
postcontentslider.php => The main file of plugin. It calls some necessary hooks.
plugins/css
main.css => Has only one class, which turns absolute and hidden all the posts before starts to slide them
plugins/includes
pcs_post_templace.php => This plugin works with ajax requests and creates new li elements dinamically. This file is the structure of the posts on the widget.
pcs_widget_showdata.php => This is the widget class, which allows the plugin to show the information.
plugins/js
pcs_general.js => This javascript file changes the posts on the widget and make ajax requests
<h3>How it works</h3>
After installing and activating the plugin, you must use it as a widget. At the widgets area, you may configure:
1) Widget title
The title that appears above the widget content
2) Box height
This is the size of the box which contains the post slider. You can change this value through css as well.
3) Category
You can choose a category to show the posts. For example: on this widget, I want to show a slide of posts about football. Anyway, you can choose “Any” and your widget will show the last posts of all categories.
4) Posts Quantity
You can choose the quantity of posts of your slideshow. You have the option of choosing “All the posts” as well, and the page will show every single post of your blog (or of a chosen category).
4.1) Ajax
If you choose more than 10 posts (or All posts), they will not be loaded when the page is loaded. Only the first 10 posts are loaded. When the first transition is triggered, the 11th post is loaded and added to the list with ajax. When the second transition is triggered, the 12th post is loaded, etc. When all the posts are already loaded and added to the list, the plugin stops making requests to the server through ajax.
5) Exhibition time
You can choose the time (in seconds) between the transitions.
<h3>Information</h3>
Remember that you can use more than one widget with this plugin and change the properties for each one.

Post Content Slider

Post content slider - Rotate your favorite posts in a widget - Developed by Alan Hidalgo Pagoto under Polvo Digital

Mind3doM RyeBread Widgets vs Post Content Slider