This by Adam J Nowak plugin adds a widget to Buddypress that displays the friends for the current user that is logged in. They are displayed as Avatar images or as a list of your friends.
You can easily resize the avatar images and control how many of your friends display in the widget. This plugin will be expanding to include a lot more features including sorting friends in different manners.
Plugin homepage: http://hyperspatial.com/wordpress-development/plugins/buddypress-friends/