Smoothie is a shiny window border theme with round corners and colored buttons.
Smoothie-white is a shiny window border theme with straight corners and white buttons.
Props to Max Rudberg for the original SmoothStripes.
Installation notes for Ubuntu users:
This theme is not packaged for Ubuntu, but it's still easy to install. Extract the file to /home/[your_user_name]/.themes/ (note the period in .themes/), and you will be able to select it in the Appearance utility by choosing "Customize...", then the Window Border tab.