Many themes now take widgets in one or more sidebars. A widget is a small, self-contained program that can be dropped onto a sidebar from the Design ⇒ Widgets page in your Administration Panel. Please note that, as soon as you drop a widget onto a sidebar, all the “built-in” items on that sidebar will disappear.
By default, there is a number of widgets ready to use in your sidebar. Widgets are configurable from the Design ⇒ Widgets page. New widgets can be installed via the Manage ⇒ Plugins page. There you will see that a number of plugins are already activated while many others are available. You are free to activate or de-activate plugins here to achieve a great deal of customisation on your blog.
If there are other plugins you would like to have available, just mail me or leave a comment here with the URL and I’ll see what I can do.