WP Twitter Timeline plugin by ppfeufer will add a twitter timelina as a sidebarwidget to your wordpress-blog. This timeline is provided by twitter as you can see here. Now you dont need to copy and paste the code from twitter with your settings anymore, just install the plugin and set the options.
Features:
Easy install
Panel for easy configuration
Customisation via CSS in settings
Demo: http://twitter.com/about/resources/widgets/widget_profile
Download: http://wordpress.org/extend/plugins/wp-twitter-timeline/