The Widget

It can be used anywhere in templates.

Usage

 the_widget( $widget, $instance, $args ); 

Parameters

$widget (PHP class name)

WP_Widget_Archives -- Archives
WP_Widget_Calendar -- Calendar
WP_Widget_Categories -- Categories
WP_Widget_Links -- Links
WP_Widget_Meta -- Meta
WP_Widget_Pages -- Pages
WP_Widget_Recent_Comments -- Recent Comments
WP_Widget_Recent_Posts -- Recent Posts
WP_Widget_RSS -- RSS
WP_Widget_Search -- Search (a search from)
WP_Widget_Tag_Cloud -- Tag Cloud
WP_Widget_Text -- Text
WP_Nav_Menu_Widget

Archives widget

Display a monthly archive list.

the_widget( 'WP_Widget_Archives' ); 

Display drop-down list:

the_widget( 'WP_Widget_Archives', 'dropdown=1' );

Calendar widget

Displays a Calendar:

the_widget( 'WP_Widget_Calendar' );

Categories widget

Displays a list of categories:

the_widget('WP_Widget_Categories');

Display a dropdown list with number of posts:

the_widget( 'WP_Widget_Categories', 'dropdown=1&count=1' );

Links widget

Displays a list of links (blogroll) in categories:

the_widget( 'WP_Widget_Links' );

Display lists in category IDs 2 or 3:

the_widget( 'WP_Widget_Links', 'category=2,3' );

Meta widget

Display site meta. (Log in/out, admin, feed and WordPress links ):

the_widget( 'WP_Widget_Meta' );

Pages widget

Display a list of Pages:

the_widget( 'WP_Widget_Pages' );

Contents

as the heading, sort by last modified date:

the_widget('WP_Widget_Pages', 'title=Contents&sortby=post_modified',
'before_title=&after_title=');

Recent Comments widget

Display to a list of recent comments:

the_widget( 'WP_Widget_Recent_Comments' );

Recent Posts widget

Display to a list of recent posts:

the_widget( 'WP_Widget_Recent_Posts' );

RSS widget

Display a list of entries from any RSS or Atom feed:

the_widget( 'WP_Widget_RSS', $instance, $args );

Search widget

the_widget( 'WP_Widget_Search' );

Tag Cloud widget

the_widget( 'WP_Widget_Tag_Cloud' );

Text widget

the_widget( 'WP_Widget_Text' );

Custom Widget

Display custom widget in template:

class My_Custom_Widget extends WP_Widget
   {
      /* your code */
   }
the_widget( 'My_Custom_Widget' );