Creating Dynamic, User-Editable WordPress Widgets
Here we’ll cover creating a dynamic widget: one that accepts, formats, and displays user input.
All You Need to Know About Making Widget Areas in WordPress Themes
Some of the best features of WordPress are the ways in which any user, once he or she learned the WordPress interface, can quickly change complex site features. Sidebar widgets are a great example — and one which is increasingly used and useful across many other areas of a WordPress site besides the sidebar. With a little dragging-and-dropping, you can quickly and easily change the appearance of your site.