Here is the link for a small tutorial:
For example, Feedburner, now has Blogger Widget. If you want to add feedburner links to your blogger blog, you do not need to add its code manually. All you have to choose add Widget from Feedburner site, give the Blogger URL, and that widget will get inserted as Page Element in your Blog.
You can see many Blogger blogs with Widgets having link "install this widget in your blogger blog". May be, in future, bloggers socialize more with their widgets! Widgetbox is one such service that has served different kind of 17,729,706 widgets (most for My-space) so far and still counting.
Simple? Yep, Widgets do make our life simple.
Source : Blogger Buzz