I would like to add a little icon for flickr, facebook, twitter, and possibly some others.
The choices we can make for using social bookmarking icons on wordpress.com blogs are found here > http://onecoolsitebloggingtips.com/2010/04/08/social-bookmarks-for-wordpress-com-blogs/
This is the link to information & instructions for the Tag Cloud widget which will display up to 45 entries > http://en.support.wordpress.com/widgets/tag-cloud-widget/
This is the link to the main page for all available widgets and you can use the links there to get information & instructions for individual widgets you may want to use. > http://en.support.wordpress.com/topic/widgets-sidebars/
If you prefer you can even change themes very easily. You can use the search utility and Feature Filters in your Dashboard > Appearance > Browse Themes > Feature Filters to locate themes of interest to you. (A-Z, Popular, Features)
Each theme has a thumbshot and a features summary description. You can browse and when you find one of interest you can click “Preview”. When you are ready to make your selection you can click “Activate”.
Hope this helps. :)